CNN  — 

The expected twin Georgia runoff elections in January that will determine control of the Senate encapsulate the structural challenge facing Democrats as they battle to secure a majority in the chamber that could determine the shape of Joe Biden’s presidency.

As the results of Senate contests increasingly correlate with the outcomes of presidential races in the same states, Democrats face the stark reality that more states lean toward the GOP in the contest for the White House.

CNN’s election center

Despite record fundraising and torrential spending from candidates such as Jaime Harrison in South Carolina, Theresa Greenfield in Iowa and Cal Cunningham in North Carolina, no Democratic challenger this month has captured a Republican-held Senate seat in a state that backed Donald Trump in the presidential race (pending the results in Alaska, where Republican Sen. Dan Sullivan and Trump both lead comfortably as the final ballots are tallied, and North Carolina, where Sen. Thom Tillis and Trump hold slim but steady leads). So far, the only Democratic Senate pickups have come in Colorado, which CNN has projected Biden to win, and Arizona, where the former vice president leads narrowly in the final counting.

The Democrats’ failure so far to oust any Republican senator in a state that supported Trump this year underscores the thin pathway the party faces toward winning Senate majorities in an era of widening partisan polarization and GOP dominance of smaller, preponderantly White states across the nation’s interior. Even though Democrats have now won the popular vote in an unprecedented seven of the last eight presidential elections, slightly more states have voted mostly for Republicans, rather than Democrats, in those contests.

Narrowing the lens to the most recent presidential races clarifies the Democratic dilemma in the Senate. Assuming Biden and Trump win every state where they are now leading, Democrats will control a commanding 39 of the 40 Senate seats in the 20 states that voted against Trump both times, with Susan Collins in Maine, who won a surprisingly comfortable reelection last week, the only exception. But 25 states have now apparently voted both times for Trump, and Republicans hold a crushing 47 of their 50 Senate seats.

That means to win a majority Democrats must nearly run the table in the five states that voted for Trump in 2016 but apparently fell to Biden this year. That list includes Georgia, a state that vividly underlines the geographic puzzle the Senate now presents for the party.

The state is rapidly changing and both parties expect the twin runoff elections anticipated in January to be competitive. But Republicans have reigned in the state for a generation, and Democrats have not elected a senator in Georgia since 2000, when Zell Miller, a conservative former governor, won a special election. Now, to secure a Senate majority that will determine the fate of Biden’s agenda the party’s only chance is to elect two, on a single day in January.

“The fundamental problem about the Senate for Democrats remains and it’s not going away anytime soon,” says Brian Fallon, a former Democratic Senate leadership aide who’s a founder of the group Demand Justice, which advocates liberal changes on the courts and in the Senate.

Republican hopes of dislodging Democratic senators in Michigan and Minnesota – two states Biden carried – were also dashed last week. But the GOP presidential advantage in more states, particularly the thinly populated ones across the Plains and Mountain West, means the party is better equipped to thrive in a world where split-ticket voting has grown much more uncommon.

“The Senate is so tough for Democrats because the Senate so overrepresents these sparsely populated rural states,” says Alan Abramowitz, an Emory University political scientist who has extensively studied the relationship between presidential and congressional voting.

Return to straight-party votes

The tightening connection between the outcomes in presidential and Senate races represents a return to the patterns that existed through the first half of the 20th century, but then loosened during much of the second half. In the early 20th century, another highly partisan era, Republicans controlled fully 96% of the Senate seats in the states that voted for William McKinley and then Theodore Roosevelt in the 1900 and 1904 presidential elections, according to calculations I performed for my 2007 book, “The Second Civil War.”

Democrats similarly controlled almost 90% of the Senate seats in the states that voted for Franklin D. Roosevelt in 1932 and 1936. Even as late as 1964, Democrats held three-fourths of the Senate seats in the states that backed John F. Kennedy and then Lyndon Johnson in the 1960 and 1964 presidential contests.

The relationship between presidential and Senate results then rapidly loosened. Republicans controlled only about half the Senate seats in the states that voted both times for both Richard Nixon in 1968 and 1972, and then Ronald Reagan in 1980 and 1984. The biggest reason for the change was that conservative Southerners who voted Republican for president continued to support Democratic House and Senate candidates, while moderate coastal Republicans made the inverse choices.

But the current started to reverse in the 1990s; as the partisan divide between the two parties widened in Congress, voters responded by reverting toward greater party-line voting in presidential and Senate (as well as House) races. After 1996, Democrats controlled two-thirds of the Senate seats in the states that twice backed Bill Clinton; after 2004, Republicans held three-fourths of them in the states that twice backed George W. Bush; after 2012, the share crossed four-fifths for Democrats in the states that twice backed Barack Obama. The modern twist on this pattern is the party that’s out of the White House now also dominates Senate seats from the states that consistently vote against the president; Republicans, for instance, held just over three-fourths of the Senate seats from states that twice opposed Obama.

The intense polarization of the Trump years has pushed these trends near their theoretical limits. Pending the results in Georgia and allowing for them retaining the Alaska and North Carolina seats, Republicans now hold 94% of the Senate seats in the states that voted both times for Trump and Democrats hold 98% of the seats in the states that twice opposed him. (Excepting Georgia, Democrats lead 6 to 2 in the four states that voted for Trump in 2016 and have apparently voted against him now.)

In 2016, for the first time since the direct election of senators began in 1918, every Senate race finished the same way as the presidential contest in that state. So far this year every race has followed that pattern as well, except for Collins’ victory in Maine.

That number might increase if Trump overtakes Biden in Arizona, since Democrat Mark Kelly has already won there, and Georgia represents a kind of asterisk on these results – since it’s not certain yet whether Biden has carried the state or how their Senate races will fall out. But the longer-term trend toward fewer mixed results is clear: As recently as 2008, six senators from both parties (including Collins) won Senate races in states that backed the other side for president.

Senate Minority Leader Chuck Schumer, D-N.Y., center right, meets with Sen.-elect John Hickenlooper, D-Colo., left, Sen.-elect Ben Ray Luján, D-N.M.,and Sen.-elect Mark Kelly, D-Ariz, in Washington on Monday, November 9.

“We’re a parliamentary system now,” says Republican pollster Gene Ulm. “Like, man, she [Collins] is the exception to the rule.”

In yet another measure of this hardening division, Lee Drutman, a senior fellow in political reform at New America, a centrist think tank, tweeted this week that pending the remaining results, only six states are expected to have Senate delegations split between a Republican and a Democrat. That’s the smallest number of split delegations since 1908, he reports.

The election results underscore the inability of Senate candidates on either side to swim much against the current of the presidential race in their states. The only Democratic Senate candidates in competitive races who won at least 1.9 percentage points more of the vote than Biden did in their states were Steve Bullock in Montana, Amy McGrath in Kentucky and Sen. Doug Jones in Alabama – and all three still lost decisively in states where Trump romped.

For all the enormous sums they spent, Greenfield in Iowa and Harrison in South Carolina each ran less than a percentage point better than Biden in their states; despite Cunningham’s massive spending, he’s running almost 2 points behind Biden in North Carolina. The only Republican Senate candidates who ran at least 2 percentage points better than Trump were Sen. Cory Gardner in Colorado and Mark Ronchetti in New Mexico, and both of them lost decisively in states Biden won easily.

More typical was the experience of John James in Michigan, the most touted GOP challenger of the cycle: He ran only 0.4 percentage point better than Trump as of the latest results and lost to Democratic Sen. Gary Peters. Only Collins, who ran over 7 percentage points ahead of Trump, truly separated from the presidential ticket.

Joe Trippi, the chief strategist for Jones, told me that Trump polarized the electorate in a way that made victory almost impossible not only for Jones, but also for all of the Democrats running in red-leaning states. In particular, Trippi said, the massive turnout Trump generated again from small-town and rural Whites swamped Democratic Senate candidates, who could not win over more than a sliver of those voters against the propulsive power of Trump’s polarizing attacks on Democrats.

“Whether it’s ever going to be possible to breach that I don’t know, but he did an incredible job of making that an impossible task,” Trippi said.

Republicans retain the advantage

Patrick Ruffini, a Republican strategist, posted a map of the results that suggested Republican Senate candidates got the best of both worlds. While most of them ran slightly behind Trump’s margins among rural voters, they still benefited from the huge turnout he inspired. On the other side, Ruffini’s analysis showed that the GOP candidates, while facing big deficits in metropolitan areas, frequently didn’t lose them by quite as much as Trump did. In North Carolina, for instance, Tillis, who leads pending the final count, lost the counties centered on Charlotte, Raleigh and Durham by about 75,000 fewer votes than Trump did at last tally.

Republicans “benefited from [Trump’s] bananas turnout in rural areas, but a lot of them still captured the [Mitt] Romney suburban voter that voted for Biden at the top of the ticket,” says Fallon, a former communications director for Senate Minority Leader Chuck Schumer, a New York Democrat.

How this dynamic plays out in the two Georgia runoffs will probably determine control of the Senate. Neither party is entirely confident how the previously Republican-leaning suburban Atlanta voters who repudiated Trump will vote in the Senate runoffs. They could break to give Biden a Senate majority to implement his agenda or prefer to provide Senate Majority Leader Mitch McConnell of Kentucky with the votes to constrain the President-elect. (One worrisome sign for Democrats is that Republican Sen. David Perdue, like Tillis in North Carolina, ran somewhat better than Trump in these suburbs last week.)

Democrats have struggled to turn out Black voters in earlier Senate runoffs in Georgia, though they are optimistic that the presence of the Rev. Raphael Warnock, who is African American, in one of the contests, and the robust get-out-the-vote machinery built by former Democratic gubernatorial candidate Stacey Abrams, will largely rectify that problem. Republicans, in turn, worry that some rural voters who surged to the polls for Trump might be dispirited by his loss and stay home.

Win or lose, the fact that Democrats must sweep the two Georgia Senate seats to reach even a 50-50 Senate split after an election that Biden will probably win by well over 5 million in the national popular vote underscores the long-term squeeze Democrats face in the body. No Democrat has held one of Georgia’s Senate seats since Miller stepped down in 2005. In the two Senate races immediately before this year’s contests (2014 and 2016), Democrats didn’t exceed about 45% of the vote.

To Fallon, the Georgia challenge underscores the need for Democrats to focus on the structural obstacles the Senate presents them. When the party next has unified control of government, he says, it must prioritize adding the District of Columbia and Puerto Rico as states, if their residents want it (the issue was on Puerto Rico’s ballot again last week). Like other liberal activists, he argues that’s the only way to begin addressing the rural imbalance that means Democratic senators next year will represent a clear majority of the population (assigning half of each state’s population to each senator), but possibly still not control the majority in the chamber.

Drutman told me in an email that even if Republicans win both Georgia seats and hold a clear majority, they will represent about 47% of the population in the next Senate, down from 48% now. If Republicans lose both Georgia seats (but hold the other states where they are now leading), he notes, they will still hold half of the Senate seats while representing less than 44% of the total population.

Far more than failings of any individual candidate or campaign, those numbers capture the real Democratic challenge in the Senate. Each time Democrats fail to win the Senate majority, Fallon notes, the party analyzes how it fell off “the tightrope” of trying to assemble a winning coalition in Republican-leaning states by “fending off these socialism attacks and motivating a base that is multicultural at the same time you are trying to not offend non-college Whites.”

Those postmortems, he says, don’t recognize that the failures aren’t primarily the results of tactical choices but “a function of malapportionment” that magnifies the influence of small rural states in the Senate. Democrats, he says, “can repeatedly have the same postmortem conversations … or we can observe that we’ve won the popular vote nationally In seven of eight presidential elections and maybe we should pursue structural reforms that don’t entrench minority rule as much as the current [Senate] system does.”

The paradox is that to change the small-state bias and other regional dynamics benefiting Republicans in the Senate, Democrats must first overcome them. And, fittingly, that effort now comes down to Georgia, the state that, when all the votes are counted, may have divided most closely last week between the red and the blue.