Kelly Ayotte said she won’t vote for Donald Trump. Joe Heck urged him to drop out altogether. Officials in both parties expect that, by Monday, most vulnerable Republican candidates will have declared they no longer back their own party’s presidential nominee.

And it’s all happening less than a month before Election Day.

Welcome to the Republican Party’s down-ballot nightmare.

A party that thought it had successfully navigated the Trump dilemma is instead reeling from the revelation that Trump bragged, on tape, about sexually assaulting women in 2005. Now, in the home stretch of their campaigns, vulnerable House and Senate Republicans are being forced to condemn their party’s standard-bearer as unfit for the White House — an event with no precedence in the history of modern American campaigns.

“I believe our only option is to formally ask Mr. Trump to step down and allow Republicans the opportunity to elect someone who will provide us with the strong leadership so desperately needed and one that Americans deserve,” said Heck, a three-term congressman and the Nevada GOP nominee for Senate. “Today, I stand here disappointed in our choices for president but more committed than ever to bringing that same code of honor, decency and respect to the United States Senate.”

Heck and New Hampshire Republican Sen. Ayotte were the first election-seeking senators to abandon Trump. (They have since been joined by numerous other Republican elected officials from across the country.)

Strategists in both parties now believe that most of the GOP candidates locked in tight races — including Sens. Patrick J. Toomey of Pennsylvania, Richard M. Burr of North Carolina, and Ron Johnson of Wisconsin — will likely follow and make similar announcements if Trump can’t quickly salvage the situation. (Roy Blunt, running in red-state Missouri, reaffirmed his support for Trump on Saturday.)

Time for a magic trick?

“Unless Trump pulls a rabbit out of a hat tomorrow night this isn’t the last you will see of Senate Republicans pulling their support,” said one Republican Senate strategist. “These things tend to have a domino effect.”

The strategists said, at this point, most Senate Republicans were inclined to withdraw their support.

The Trump implosion is deeply disappointing to Republican officials, who as recently as Friday were confident they had devised a successful strategy to navigate Trump: Condemn his frequent provocations, reaffirm he’s a better choice than Hillary Clinton, and quickly change the subject.

They believed it was the only way to keep Trump’s core supporters happy while not alienating moderates. And although Trump was a drag on the ticket, the strategy appeared to be working: The GOP had a chance to retain its Senate majority and stave off heavy losses in the House — to the surprise of even some Republican operatives.

“I don’t see a wave,” said Scott Reed, senior political strategist for the Chamber of Commerce, during an interview Thursday. “I see these races as all one-offs.”

Now, if they all choose to renounce their support, GOP lawmakers will have to worry about the effect on Trump loyalists, who constitute a sizable chunk of the Republican base.

That tension was evident when Heck announced during a rally in Las Vegas that he wouldn’t support Trump. On a live stream of the event, at least two people were heard booing the congressman.

A spokesman for the Heck campaign said only two of the 200 people gathered did so, but Republican strategists have long worried that distancing themselves from the New York billionaire would persuade many of his supporters to not cast a ballot for Senate races.  

Politics vs. principle

Even when they do withdraw their support from Trump, Republicans will still face criticism from Democrats that their decision was rooted in politics and not principle.

Why, Democrats will ask, did it take so long for Republicans to stop supporting a candidate who has frequently offended women, and religious and racial minorities before?

“Sen. Ayotte’s career has been one political stunt after another, and today’s decision is no different,” said Tom Lopach, the executive director of the Democratic Senatorial Campaign Committee. “Just days after calling Trump a ‘role model,’ she is now attempting the most politically craven effort at self-preservation that we’ve seen. The time for courage has passed, and Sen. Ayotte solidified her role in Trump’s party long ago. New Hampshire voters won’t be fooled by this stunning example of politics at its worst.”