Along with the White House, the Republican Party also regained the US Senate in last week’s elections. Despite this victory, Democrats held on to seats in four states that voted for Donald Trump at the presidential level. Lauren C. Bell looks at why this year’s Senate election results are different from the presidential election results, writing that candidate quality still matters, as does the role of independent candidates. Now, she writes, House Republicans will need to choose a leader who can manage a slim and far from unified majority. 

• This article is part of ‘The 2024 Elections’ series curated by Peter Finn (Kingston University). The series has explored the 2024 US elections at the state and national level. If you are interested in contributing to the series, contact Peter Finn (p.finn@kingston.ac.uk).

Seventeen months ago, in June 2023, I previewed the 2024 Senate elections by noting that Republicans’ chances to re-take the Senate looked good but were far from certain. With the 2024 election now in the books, their return to Senate control after four years in the minority is now assured. Although at the time of this writing, votes are still being counted in Pennsylvania, the ultimate outcome there won’t affect Senate control, just the size of the Republicans’ majority.

Back in June 2023, I noted that retaining control of the Senate was always going to be a challenge for the Democrats. They had 20 seats to defend this year, compared with just 11 Republican seats being contested. The three seats that we know that Republicans successfully flipped thus far are West Virginia, Ohio, and Montana—three states where Trump defeated Joe Biden by large margins in 2020. Pennsylvania has been called by the Associated Press (AP) for Republican Dave McCormick although vote counting continues; if the AP call holds, Pennsylvania will be the fourth Senate seat that Republicans will have successfully wrested from the Democrats in this cycle—and the only one to flip in a state that Joe Biden won—albeit narrowly—in 2020.

At the same time, Democrats successfully held on to Senate seats in Nevada, Wisconsin, Arizona, and Michigan, even as Republican presidential candidate Donald Trump won in all four states.

Ticket splitting, or something else?

Kamala Harris’s loss has not only generated significant angst within the Democratic Party, it has also sparked conspiracy theories from some left-leaning voters. These claims use the Democrats’ Senate victories in states where Trump won to make suggest malfeasance in the presidential contest. But there is no evidence of voter fraud, vote tampering, or of a rigged election.

There are any number of logical explanations for why this year’s Senate results are different from the presidential election results. One such explanation that the national media has offered is ticket-splitting. For example, a Washington Post election post-mortem declared: “Normally, the party suffering a multimillion-ballot loss in the popular presidential vote would suffer in lower-profile downballot races, but enough voters in critical battlegrounds split their tickets to avoid a full Democratic wipeout.”

I’m skeptical of the ticket-splitting claim; given people’s growing positive sentiments for the party they support and negative feelings for the other (known as affective polarization) and exit poll results suggesting that roughly 95 percentage of partisans voted for their party’s nominee. Instead, I think Senate-specific candidate factors and the relatively lesser influence of minor party candidates on electoral outcomes in Senate races can better explain the seemingly-but-not-actually odd outcomes fueling conspiracy theories on the left.

As Table 1 below reveals, in most of the 31 states with Senate elections this fall, the Democratic candidate (or the Independent candidate, in Maine and Nebraska) overperformed—and in some cases, significantly overperformed—the Democratic presidential candidate. But there were a handful of states—Indiana, Maryland, Massachusetts, Mississippi, and Tennessee—where Harris overperformed the Democratic senatorial candidate. In all these cases, including in the swing states, candidate- or election-specific factors largely explain the outcome.

Table 1 – Comparing Senate and Presidential Election Results

†States where the principal challenger was an Independent. Green states are those where the Senate Democratic candidate overperformed Harris. Red states are those where the Senate Democratic candidate underperformed Harris.

Credit: Scrumshus [Public domain]

Candidate quality is still important

Back in that June 2023 blog post, I wrote: “Republicans’ ultimate success will depend on their ability to nominate quality candidates for each race, something they’ve struggled with in recent elections.” In at least two of the closest contests, Republicans’ choice of candidate hurt their ability to capitalize on what turned out to be higher-than-expected enthusiasm nationally for Trump.

In Nevada, for example, Democrat Jacky Rosen received almost exactly the same number of votes as Kamala Harris—but Republican candidate Sam Brown significantly underperformed relative to Trump, resulting in Rosen defeating Brown even as Trump defeated Harris. Similarly, in Michigan, both Senate candidates received fewer votes than their respective presidential co-partisan candidates did, but Republican Mike Rogers underperformed Donald Trump by a much larger margin than Elissa Slotkin underperformed Kamala Harris.

In Wisconsin, minor party vote consolidation seems to explain why incumbent Senator Tammy Baldwin overperformed Kamala Harris by just enough to eke out a win over her Republican challenger even as Harris was narrowly defeated. Importantly, there were far fewer minor party candidates on the Wisconsin Senate ballot than there were on the presidential one.

This pattern was also evident even in states where the presidential and Senate results aligned. Take Virginia, where Kamala Harris won but where Democratic Senator Tim Kaine received 78,521 more votes than she did and outperformed her 51.7 win percentage by securing 54.1 percent of the vote in the Senate race. Harris and Trump were joined at the top of the Virginia ballot by Jill Stein (Green), Chase Oliver (Libertarian), and two independent candidates, Claudia de la Cruz and Cornel West. Virginia voters also can write in their preferred candidate if that person’s name doesn’t appear on the ballot. Thus, Virginia voters had seven choices for President. In the Senate race, however, only two names appeared: Kaine, the Democratic Party candidate and Hung Cao, the Republican Party candidate. While voters could still write someone else in, fewer than 7,900 voters did so. Although he managed 78,521 more votes than Harris did, this was still less than the 91,000 minor party and write-in votes that were cast at the top of the ticket.

The only Senate race where ticket-splitting appears plausible was in Arizona, where Democratic Party Senate candidate Ruben Gallego outperformed Harris by about 90,000 votes, but where Republican Party candidate Kari Lake underperformed Trump by about 150,000 votes. Lake remains a polarizing figure in Arizona; she ran for governor there in 2022 but refused to concede, and there is anecdotal evidence to suggest that her 2022 stolen election claims hurt her in her efforts to succeed Democratic Senator Kirsten Sinema, who did not run for reelection.

Notably, ticket splitting also appears to have happened in North Carolina, where there was no Senate race but there was a statewide contest for governor. Democratic Party candidate Josh Stein significantly overperformed Kamala Harris, winning more than 350,000 more votes than she did, and winning several rural counties where, as one local newspaper noted, “it feels unheard-of for voters not to support the Republican nominee.” But Stein was aided by the fact that his opponent, Mark Robinson, who once called himself a “black Nazi” in an online pornography chatroom, turned out to be one of the most unelectable candidates in political history.

What’s ahead for the Senate in the 119^th Congress? 

With control of the chamber assured, Republicans now face the challenge of organizing. A trio of Republicans—Texas senator John Cornyn, South Dakota Senator John Thune, and Florida Senator Rick Scott—are vying for the role of Senate majority leader, a post that was held by Kentucky Senator Mitch McConnell the last time Republicans controlled the chamber. Earlier this year, McConnell announced that he would step aside from a leadership role following this year’s elections; he has spent the last four years as Senate minority leader and over 17 in the Republican senate leadership. Scott has aligned himself closely with Trump; Cornyn and Thune have been more reticent to embrace the President-elect.

Even with controlling the majority, the Republican Senate is far from wholly unified. Maine Senator Susan Collins and Alaska Senator Lisa Murkowski both have been publicly critical of Trump. Collins declared she would not vote for him and Murkowski has previously hinted that she would consider leaving the Republican Party if it continued to embrace him. North Carolina Republican Thom Tillis has just two years before he will stand for reelection in a closely divided state, which may moderate his behavior.

How things play out in the Senate will also depend, in no small part, on the ultimate partisan makeup of the House of Representatives. The Republicans are almost certain to retain control of the House, giving them a partisan ‘trifecta’ that in theory should allow them to accomplish their policy objectives. But 2024 was not a wave election; House Republicans are likely to control only the slimmest majority, which will have implications for the House’s legislative productivity and will affect what the Republican party is able to accomplish.

What is certain, however, is that the Republican Senate will renew its laser-like focus on confirming judicial nominations. The last time Republicans controlled the chamber, between 2017 and 2020, McConnell prioritized judicial confirmations above virtually all else. The Senate has remained a “legislative graveyard” ever since.

This is at least in part why President-elect Trump has called upon the Senate to eliminate its legislative filibuster, but at least for the time being, the procedural tactic—which requires 60 votes to overcome—will be a bulwark against the Republicans’ ability to steer many of their policy proposals through Congress. Whether the legislative filibuster survives the next Congress, or the Republicans ultimately capitulate to Trump and eliminate it through procedural fiat, remains to be seen, and is another reason to keep an eye on the Senate as the 119^th Congress begins.

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