Sinema, her fundraising fading, faces a ticking clock over the Senate decision

Mr. Tester's main Republican challenger, Tim Sheehy, a wealthy businessman, announced that he had raised $2.5 million in the fourth quarter, including $450,000 of its own money. Republicans also expect Rep. Matt Rosendale, a far-right agitator, to enter the race soon.

In Ohio, Senator Sherrod Brown, a Democrat who is also seeking his fourth term, raised $6.6 million in the fourth quarter and had $14.6 million on hand, according to his campaign.

Among the top three Republicans seeking their party's nomination in Ohio, Bernie Moreno, a businessman known for his chain of car dealerships in the state, gathered $800,300 during the fourth quarter and ended the year with about $2 million in cash, his filing shows. Mr. Moreno, backed by former President Donald J. Trump, spent $3 million on his own campaign last year and added another seven-figure check this month, according to a person familiar with the matter who was not authorized to discuss to speak in public. .

Another Republican candidate, State Senator Matt Dolan, made this point $357,700 during the fourth quarter and started the new year with $4.8 million on hand, its reports showed. The GOP's third major candidate, Secretary of State Frank LaRose, rallied $812,500 during the fourth quarter and started the new year with $771,600 in the bank, according to his refills.

Much of the tension in the battle for the Senate, however, centers on Ms. Sinema. Since leaving the Democratic Party in December 2022, she has been ambiguous about her plans for a second term, leaving the political establishment on a knife's edge.