With Control of the Senate in Play, These Are the Races to Watch

With the Senate knotted at 50-50 for each party, Republican control is only one seat away. But this election season has been full of surprises.

For much of the campaign season, Democrats have appeared ready to grab a Republican seat in Pennsylvania, meaning Republicans would need to flip two Democratic seats to earn a majority. But recent fumbles by Republican candidates in New Hampshire, Georgia and Arizona have made finding those two winnable races more difficult.

Here are the seats where each party is vulnerable.

Cook Political Report Race Ratings
for Current Senate Seats

Republicans
Currently hold 50 seats, need 51 for majority

Democrats
Currently hold majority with 50 seats (vice president casts tie-breaking vote)

Republicans not up for re-election

Solid R

Likely R

Lean R

Tossup

Democrats not up for re-election

Solid D

Lean D

Tossup

Republicans not up for re-election

Democrats not up for re-election

Earlier this year, Senator Raphael Warnock, a Democrat in Georgia, had been considered one of the Senate’s most vulnerable Democrats as he took on Herschel Walker, a scandal-prone Republican backed by former President Donald J. Trump. Then came the accusation that Mr. Walker, a staunch opponent of abortion, paid for an ex-girlfriend’s abortion, and the race turned upside-down.

Cook Political Report still rates the contest a tossup, but the new allegations have given Mr. Warnock an edge and put Mr. Walker on the defensive.

A Democratic seat in Arizona may have at one point been vulnerable. But the enduring popularity of the incumbent, Mark Kelly, and the faltering campaign of his challenger, Blake Masters, may put it out of Republican reach.

The race in Nevada might be the Republicans’ best chance to take a seat from the Democrats. Catherine Cortez Masto, the incumbent, is not well established in a state known for its transient population and fickle voters, especially in midterm elections.

But her Republican challenger, Adam Laxalt, the state’s former attorney general, lost his run for governor in 2018 and has yet to open a clear lead.

The Democrats’ best chance to pick up a Republican seat is in Pennsylvania, where Senator Patrick J. Toomey is retiring. The celebrity physician Dr. Mehmet Oz won the Republican nomination, helped by Mr. Trump’s endorsement, but he did not have the love of the Republican base.

His opponent, Lt. Gov. John Fetterman, had a life-threatening stroke that gave Dr. Oz an opening. The evident effects of the stroke, and the Republican’s attacks on Mr. Fetterman as a criminal-coddling liberal, have narrowed the race.

Democrats had high hopes of unseating the Republican senator from Wisconsin, Ron Johnson, six years ago and were stunned by his relatively easy re-election. Since then, Mr. Johnson has become the Senate’s leading peddler of conspiracy theories and Covid-19 misinformation, yet he is hanging tough against Wisconsin’s lieutenant governor, Mandela Barnes, who comes from the Democrats’ liberal wing and has proven vulnerable to attack, especially on crime.

A sleeper race for the Senate is also the sleepiest. Representative Ted Budd, a North Carolina Republican backed by Mr. Trump, has tried to lie low and ride the national current to the seat of Richard M. Burr, a Republican who is retiring.

Cheri Beasley, a former chief justice of the North Carolina Supreme Court, is running as a judge above the political fray. North Carolina is a state that has broken Democrats’ hearts, and it could well do so again. But Mr. Budd and Ms. Beasley are consistently polling at a tie.

Despite the challenges ahead, Republicans still have plenty of ways to win Senate control. They could beat Senator Catherine Cortez Masto in Nevada and push Senator Raphael Warnock to a runoff in Georgia. They could overwhelm the Georgia race with cash to rescue Mr. Warnock’s opponent, Herschel Walker. They could also pull off a come-from-behind win in Pennsylvania.

But Democrats have options as well. If they can seal a victory in Pennsylvania and defeat Senator Ron Johnson in Wisconsin, it’s hard to see a way for Republicans to take three Democratic seats to compensate.