If you want to understand the recent history of the Republican Party, you could do worse than to look at the differing trajectories of two past presidential candidates — Sen. Mitt Romney of Utah and Sen. Marco Rubio of Florida. I was an unpaid foreign policy adviser to both men: for Romney in 2012 and Rubio in 2016. After their votes on impeachment — Romney was the lone Republican to vote for conviction (on the abuse-of-power charge), while Rubio joined the rest of his party in acquitting President Trump despite overwhelming evidence of his guilt — I felt prouder than ever of my work for Romney and more ashamed than ever of my work for Rubio.

This is not an outcome I could have predicted, any more than I could have predicted that a former reality TV star with scant knowledge of government and even fewer morals would take over the party of Lincoln — and indeed the whole country.

When I labored on the Romney campaign, I, like many “movement conservatives,” was lukewarm about a candidate I viewed as being insufficiently ideological. Romney had pivoted from being a moderate governor of Massachusetts to a “severely conservative” presidential candidate, but his transformation always appeared a bit insincere. He seemed like the second coming of Michael Dukakis: competent but uninspiring. Rubio, by contrast, set conservative hearts aflutter because he seemed to be a true believer with a preternatural gift of communication. Some saw him as the second coming of Ronald Reagan.

During the 2016 primaries, both Romney and Rubio were scathing in their denunciations of Trump. “Here’s what I know: Donald Trump is a phony, a fraud," Romney said. “His promises are as worthless as a degree from Trump University.” In a similar vein, Rubio called Trump a “con artist” who was perpetrating “the biggest scam in American political history” and couldn’t be trusted with the nuclear codes.

After Trump became the Republican nominee, Rubio endorsed him; Romney did not. But Romney interviewed to be secretary of state and accepted Trump’s endorsement in his 2018 Senate campaign. In the Senate, both men have voted with the president most of the time — Rubio 90.4 percent, Romney 78.8 percent. Both men are religious — Romney is a Mormon, Rubio a Catholic — and both share many of the same conservative views.

But the impeachment vote revealed the night-and-day difference between them: Romney is a man of principle and Rubio is a typical politician. In other words, the truth is exactly the opposite of what I had once assumed.

Rubio explained his vote against witnesses and the articles of impeachment with a mealy-mouthed, unconvincing statement in which he claimed he could not impeach “even if I assumed the President did everything the House alleges,” because to do so would simply exacerbate “the bitter divisions and deep polarization our country currently faces.” This rationale makes no sense because if Rubio, as a Republican, crossed over to vote for Trump’s impeachment, that would by definition lessen the partisan divide.

That’s precisely what Romney did in a riveting speech on Wednesday that was full of courage and conviction. “Were I to ignore the evidence that has been presented, and disregard what I believe my oath and the Constitution demands of me for the sake of a partisan end, it would, I fear, expose my character to history’s rebuke and the censure of my own conscience,” Romney said.

He was almost moved to tears as he was speaking — and so was I. How extraordinary to see a single Republican doing what was right even though he knew it would be intensely unpopular with his party. Indeed, it did not take long for Trump to post an attack video on Romney, for Donald Trump Jr. to call for Romney to be expelled from the Republican Party, and for Fox Business host Lou Dobbs to equate Romney with Judas, Brutus and Benedict Arnold. (Wasn’t Brutus a hero — “the noblest Roman” — for killing a tyrant?) It is the fear of such attacks that has led Rubio and all the other Republicans in Congress to fall into line behind a dangerous demagogue. Not Romney. He stands on principle, a man alone and unafraid, and in so doing he exposes the shameful cowardice of his Republican colleagues.

This turn of events makes me regret that Romney never became president and hope that Rubio never will be. “I will tell my children and their children that I did my duty to the best of my ability, believing that my country expected it of me,” Romney said. What will Rubio tell his children, I wonder? That he had to shirk his duty so that he could preserve his political viability?

That Rubio is a Republican prince and Romney a Republican pariah tells you all you need to know about how low a once-proud party has sunk.

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