The five most important Senate races to watch in 2024

In less than two weeks, the 2024 presidential election will begin with the Republican Iowa caucus. Former president Donald Trump will likely dominate in the heavily white churchgoing state. Meanwhile, President Joe Biden faces no legitimate challenge in the Democratic primary despite concerns about his age and low approval numbers.

But just as important as who wins the White House will be the makeup of the Senate, which will determine what types of cabinet officials and judicial nominees can be confirmed.

In 2022, Democrats staved off the worst possible outcomes when they held all of their Senate seats and Sen John Fetterman flipped Pennsylvania’s Senate seat for them, giving them a 51-seat majority. Republicans for their part nominated a slew of unelectable candidates, many of whom won their primaries thanks to Mr Trump’s endorsement.

This time is different. Democrats are defending Senate races in eight swing states. Three of them — Montana, West Virginia and Ohio — are in which Mr Trump won twice. Another four —Arizona, Pennsylvania, Wisconsin and Michigan —are in states that he won in 2016 but lost in 2020. Another is taking place in the perpetual swing state of Nevada. That means that even if Democrats won races in all the states Mr Biden won in 2020 and Republicans won all the states Mr Trump won, Republicans would still control the Senate by three seats.

In 2022, Inside Washington regularly put out lists of the top five Senate races. Given that West Virginia will almost certainly flip, we are changing the format to show you the most important Senate races to watch. Here are your five races that will determine the balance of the Senate.

1. West Virginia

There is no other way around it. Sen Joe Manchin’s (D-WV) decision to not seek re-election--and potentially engage in a quixotic third-party run for president--means that he will likely be the last Democrat elected from the heavily white state that relies heavily on the coal industry for at least a generation. After years of beating the odds by selling himself as a different type of Democrat, Mr Manchin’s luck ran out after he co-authored the Inflation Reduction Act, a massive bill focused on climate change and health care. Mr Biden’s signature of the law meant he could no longer differentiate himself from the rest of the party. Republicans got the candidate they wanted when Gov Jim Justice--Mr Manchin’s former friend who switched parties thanks in part to Mr Trump--announced last year that he would run. This will be the last time this list will cite West Virginia since Mr Justice will almost certainly become the next senator from the Mountain State.

2. Ohio

Mr Manchin’s exit means that Republicans will target the two other Democrats in a state Mr Trump won twice. Sen Sherrod Brown (D-OH), a populist Democrat who has used his perch on the Senate Banking Committee to criticise Wall Street, has largely gotten lucky that he’s run in years that were good for Democrats such as 2006, 2012 and 2018. But Mr Trump won Ohio by eight points in 2020, meaning Mr Trump would simultaneously need to underperform in Ohio and Mr Brown would need to over-perform. Right now, the Republican field is split with multiple candidates, including Secretary of State Frank LaRose, state senator Matt Dolan and businessman Bernie Moreno. Last month, Mr Trump endorsed Mr Moreno, an arch-conservative whom Sen JD Vance endorsed. On Wednesday, the political action arm of the conservative Club for Growth also endorsed Mr Moreno.

3. Montana

In truth, Montana or Ohio could switch spots on this list. In fact, Mr Trump won the largely rural Montana by double digits. The state’s Democratic Sen Jon Tester has long positioned himself as a unique brand of Democrat thanks to his work as a dirt farmer who lost three fingers in a meat grinding accident and as chairman of the Senate Veterans Affairs Committee. But his voting record is more liberal than Mr Manchin’s. He’s pulled off miracles before, such as in 2012 when he won re-election despite Mitt Romney winning the state and in 2018 despite his voting against confirming Brett Kavanaugh to the Supreme Court. But it might be tougher this go around. The one thing he has going for him is his opponents. Rep Matt Rosendale, an archconservative whom he beat in 2018, has floated the idea of running against Tim Sheehy, a retired Navy SEAL pilot whom the GOP establishment supports. A bloody primary could lead to Mr Rosendale winning or Mr Sheehy being significantly weakened.

4. Arizona

Arizona is shaping up to be perhaps the weirdest Senate race in the country. In 2018, Kyrsten Sinema became the first Democrat to win a Senate race in Arizona in 30 years. In the years that followed, she regularly opposed her party’s legislation or blocked efforts to change the filibuster to pass voting rights. After Sen Raphael Warnock (D-GA) won his runoff race in 2022, she announced she would leave the Democrat Party to become an independent, though she would still caucus with the Democrats. Ms Sinema has not announced whether she will seek re-election, but Rep Ruben Gallego (D-AZ), an outspoken Latino progressive and retired Marine, announced he would challenge her. On the Republican side, Kari Lake, the former news anchor who lost her bid to become governor in 2022 thanks to her continued election denialism, announced she would run for the seat. Were a three-way race to happen, Ms Sinema would likely siphon votes from Ms Lake rather than Mr Gallego. But too much is unclear until Ms Sinema makes her decision.

5. Nevada

Like Arizona, Nevada will likely be one of four states that decides the presidency, alongside Wisconsin and Georgia. In 2018, Sen Jacky Rosen beat incumbent Republican Dean Heller in the Silver State thanks to the robust Democratic machine led by the late Senate Majority Leader Harry Reid. But even as Democrats have won the state in every election since 2008, their margins have reduced significantly. In addition, Sen Catherine Cortez Masto, the Senate’s lone Latina, narrowly won re-election in 2022 even as Republicans won back the governorship. So far, Republicans have largely gotten behind veteran Sam Brown, while, as friend of the newsletter Gabby Birenbaum The Nevada Independent flagged last month, Sen Tommy Tuberville of Alabama held a fundraiser for election denier and failed secretary of state candidate Jim Marchant at Mar-a-Lago. Nevada is known for tight senate races (the late Mr Reid lost his first Senate race by 624 votes and won another term by 401 votes). And the rightward drift of Latino voters helps Republicans. But anger about the Supreme Court’s Dobbs v Jackson decision might propel Ms Rosen as it did Ms Cortez Masto.