These and similar journalistic accounts provide valuable evidence to scholars of American party politics, who are currently attempting to ascertain whether party elites maintain the capacity to steer presidential nominees toward or away from favored or disfavored candidates. According to the article, Senate Majority Leader Mitch McConnell, though aghast at Trump's front-runner status, has responded by simply assuring members of his own caucus that they can separate themselves from the top of the ticket if necessary when seeking re-election this fall. Former Utah governor Mike Leavitt is quoted as saying that "there is no mechanism" by which party officials can stop Trump's candidacy. "There is no smoke-filled room. If there is, I’ve never seen it, nor do I know anyone who has. This is going to play out in the way that it will."
If "The Party" truly held the power to unilaterally prevent a Trump nomination, presumably people like McConnell and Leavitt would not only know about it, but be active participants themselves. It is more likely that Republican leaders feel as if they are largely constrained by a nomination system in which party voters exercise ultimate control, influenced by candidate strategies, media coverage, and the idiosyncratic characteristics—electoral sequence, delegate allocation rules, party caucuses—of the process itself.
To the extent that party leaders do claim to believe that some in their ranks could indeed shape the outcome of the race, they seem to be merely passing the buck with a healthy dose of motivated reasoning: it's always someone else's responsibility or someone else's fault. Hence the grousing in the article about Chris Christie's endorsement of Trump, Jeb Bush's continued neutrality, and John Kasich's persistence in the race—as if any of these individuals, who spectacularly failed at convincing Republicans to support their own candidacies, could nonetheless sway the party electorate away from Trump's much more appealing campaign.
That said, it seems as if the conventional wisdom this weekend has overstated the strength of Trump's position in the race a bit—perhaps because the press, too, is exaggerating the "game-changing" influence of Christie's endorsement. Yes, Trump can still be stopped, but it will take another candidate to step up and defeat him. At the moment, Marco Rubio seems like the only plausible competitor with the capacity to do so.
It has finally dawned on Rubio over the past few days that he will need to cut into Trump's support in order to win, and he has abruptly shifted into attack mode. Not all of Rubio's punches may land, but at last Trump is being targeted by a sustained negative broadside. It may be too little, too late, or Rubio himself may not prove a sufficiently capable candidate to prevail over Trump, but if Trump is to be stopped, Rubio is the man who needs to stop him.