The Dynamics of Governing
One of the hilarious side-effects of the collapse of the GOP into a Balkanized mob of squabbling hobgoblins is that there is no longer a defined "group" in whose best interest anyone can claim to be acting. Even that most basic of the adhesive wingnut forces -- the dogmatic belief that Libruls are the source of all evil on Earth, which has loosely bound this Team of Cavils together through good times and bad -- has begun to erode now that Donald Trump has dared to breach the Dubya Administration Containment Barrier and mention that, in fact, the Bush presidency did not begin on September 12, 2001 and that the Iraq War was a debacle that Bush lied us into.
Sure, in the abstract, everyone in a leadership position among the ruins of what was once the Party of Lincoln knows that letting Donald Trump win will doom them. But absent the countervailing force of an actual, vibrant political party capable of exerting any pressure on anyone to do anything, each individual "Republican" candidate has been free to fill the "for the good of the Party" vacuum for themselves by inventing a rational for their candidacy based entirely on the limits of their own ego, ambition and financial resources.
Which means that, based on all available evidence, most or all of them will keep right on going for the blonde, damn the consequences and pass the popcorn.