Until Christine Blasey Ford's allegations of sexual assault against Supreme Court nominee Brett Kavanaugh surfaced, it was probable that two or three red-state Democratic senators running for re-election would have voted to confirm him.

It's still possible that some Democrats will side with Republicans in the confirmation battle, but only if a handful of GOP moderates are on board. 

Politico:

The Democratic Caucus' clutch of moderate senators, who mostly hail from conservative states where voters could punish them for opposing Kavanaugh, is under more pressure than ever from a liberal base furious over the sexual assault allegations.

So most of those intently watched Democrats are deferring their public stance until after Thursday's scheduled hearing with Ford and Kavanaugh.  They're worried about taking unnecessary political risk by taking a stand amid a swirl of unproven charges and uncertainty about whether the GOP even has the votes to confirm the 53-year-old appeals court judge, according to senators and aides.

Still, Democratic leaders are confident of a unanimous "no" vote against Kavanaugh from their caucus, especially if Ford comes off as credible, according to more than a half-dozen senators and aides.

It comes down to this: no Democratic senator will go out on a political limb and support Kavanaugh unless his confirmation is inevitable.  None of those Democrats wants to be the vote that puts Kavanaugh over the top.  That means that it will be GOP moderates who hold the balance of power on the nomination.

Holding only a 51-49 advantage in the Senate, Republicans can afford to lose exactly one vote in the nomination fight.  In reality, there are still three GOP votes up for grabs, with the key senator being Maine's Susan Collins.

The other two senators – Alaska's Lisa Murkowski and Arizona's retiring Jeff Flake – will almost certainly vote with Collins on the nomination.  Democrats are aware of this and have initiated an intense pressure campaign to convince – and to threaten – Collins to vote "no."

Collins is playing it coy and will probably make up her mind after the hearing on Thursday.

The Hill:

"I think Collins will vote with us.  Kavanaugh gave her the right answer on Roe v. Wade," said a Republican senator who requested anonymity to comment on her position.

Collins told Showtime's "The Circus" in a recent interview that she "doesn't think Kavanaugh will overturn the landmark abortion rights case."

Collins said Monday that she believes Senate investigators should reach out to a second woman, Deborah Ramirez, who has accused Kavanaugh of exposing himself to her at a college party.  A Democratic aide cited her statement as evidence that she hasn't dismissed the second woman's allegation as other Republicans have. 

Some Senate veterans see Collins as a possible heir to the late Sen. John McCain (R-Ariz.), who was often considered the conscience of the Senate – or at least the Senate GOP conference.

"She has the opportunity to be the conscience on this issue," said former Sen. Ben Nelson (D-Neb.), who worked with Collins in 2005 to fashion the so-called Gang of 14 compromise on judges, and also teamed up with her in 2009 to pass a major fiscal stimulus, one of former President Obama's first legislative accomplishments.

"I always feel empathy with people who are put in that position," said Nelson, adding that he voted for the 2010 Affordable Care Act because he knew it was the right thing to do even though he knew it would cause a major political backlash.

"I just hope she does what she thinks is right," he said.  "You can't couch votes on what's best for you.  You have to couch votes on an entirely different standard and that's where conscience plays a major role.  Clearly it did for Sen. McCain."

How can any of those three senators vote "no" and expect to remain Republicans?  Sinking Kavanaugh would be a catastrophe for the GOP on so many levels.  It would more than likely blow up the midterms and open the door to significant Democratic gains.  It would make it extremely difficult for Trump to name another conservative with Kavanaugh's pedigree.  And if the GOP loses control of the Senate, it will probably mean that Democrats will oppose any nominee until at least 2021.

The fate of a conservative, constitutional Court is at stake.  Collins, Murkowski, and Flake cannot be unaware of that.  Republican voters would never forgive any of them, and the party itself might take punitive measures against them.

Unless Ford has some bombshell evidence, it's hard to see how any reasonable person can say she's "credible."  For that reason, as well as the prospect of being all but kicked out of the Republican Party if she votes "no," I expect, in the end, that Collins will reluctantly side with the majority and vote to confirm Kavanaugh.