You would be, almost certainly, totally wrong. In fact, being attacked by Romney is more likely to cement Trump's hold on the nomination than loosen his grip on it. Here's why.
Romney is the face of the establishment. He's just the sort of guy the party loves - a measured statesman who views running for office as a civic duty. He's "serious." He has "gravitas." He is "trustworthy" and "steady."
He's also the embodiment of everything Trump has built his entire campaign against. Romney is too cautious, too mannerly, not tough enough for Trump's taste. He's the face of a Republican Party that lost twice to Barack Obama. He's part of the problem, not the solution.
Rather than undercut Trump, Romney's attacks bolster him. And Trump knows it - going all in against Romney in an interview on MSNBC's "Morning Joe" on Thursday.
"He was a disaster," Trump said of Romney. "He ran one of the worst campaigns in presidential history. That was an election that should have been won by Republicans." Trump also noted that Romney "begged me for my endorsement four years ago" - an endorsement he eventually gave.
Look, I get what motivates Romney to give a speech like this one. He feels like as the party's most recent presidential nominee he has an obligation to speak out when he sees things going off the rails. And he's clearly frustrated by what he sees as the ineffectual approach to bringing Trump down that the other candidates in the race have taken. He wants to be the "adult in the room," aides keep saying. He wants to "show them how you take down a bully," his backers say.
I get it. I just don't think it will work.
While Romney may not think the Trump takedown has been executed as well as it might by the party establishment, is there ANY Republican voter paying even a little attention who doesn't get that the party poobahs don't want Trump and think he poses a major threat to the GOP? The answer is no.
Romney's speech will set off lots and lots of head nodding among the people who concluded long ago that nominating Trump is a bad idea. But will it persuade anyone who is voting for Trump not to do so? I seriously doubt it. In fact, I think that more than anything, it will confirm for those people that Trump must really be a threat to the hated establishment if people like Romney are this panicked about the real estate mogul getting the nomination.
If Trump ever needed a testament to just how much the establishment is against him, this Romney speech is it. Romney felt like he needed to do it but the most likely outcome is the opposite of what he was going for: an emboldened Trump crusading against the sad losers of the Republican Party past.
