Rep. Justin Amash (R.-Mich.) is the most subversive lawmaker in America. That’s not because he takes extreme positions. It’s because he refuses to engage in the capital’s favorite pastime: partisanship. His willingness, alone among 250 Republicans in the House and Senate, to call for President Trump’s impeachment is only the latest indication that he marches to the beat of a different drummer — one whose tune is unheard by his colleagues.

Since coming to Congress in 2011, Amash has consistently voted for his libertarian beliefs rather than for the Republican party line. I don’t agree with him on a lot of issues (he’s opposed to gun control and abortion rights), but I’m impressed that he has opposed farm subsidies, the USA Patriot Act, Trump’s ban on Muslim immigration, political gerrymandering, the Saudi war in Yemen, some aid to Israel and Trump’s border wall. He represents a district that Trump won by nearly 10 points, yet he votes with the president only 62 percent of the time — the lowest percentage of any House or Senate Republican.

This is pretty revolutionary in a Congress where bipartisanship has gone the way of tail-fin cars and rotary-dial phones. Both parties are guilty, but Republicans are guiltier. The GOP has moved much further right than the Democrats have gone left in what political scientists have labeled “asymmetric polarization.” Partisanship is a powerful, mind-altering drug, and it has warped Republican sensibilities. There has been plentiful evidence this week — just like every other week — of its corrosive effects.

Exhibit A is, of course, Trump. While in Japan, he approvingly quoted North Korean dictator Kim Jong Un calling Democratic presidential candidate Joe Biden “a low IQ individual.” It is bad enough that Trump derides his political opponents in such vulgar terms. Even worse is that Trump does so on foreign soil, where he is supposed to be representing the United States of America, not the Republican states of America. So much for the old adage that “partisan politics should stop at the waters’ edge.” Worse still, he sides with a murderous dictator over a former vice president of the United States. Any one of these offenses would have been unthinkable for any previous president. Trump does all three at once, and it’s a one-day story, because we’ve gotten so used to his outlandish behavior. Except it’s not actually so outlandish. This is the kind of name-calling that has been a mainstay of the conservative-media complex for years. Trump is just saying what Fox News viewers want to hear.

Exhibit B is Rep. Liz Cheney (R.-Wyo.), the No. 3 Republican in the House. As the daughter of George W. Bush’s vice president and George H.W. Bush’s defense secretary, and as a former State Department official herself, she might be expected to conform to traditional norms of political decorum. But no. When questioned on ABC’s “This Week” about Trump’s offensive attack on Biden, Cheney refused to criticize the president. She then parroted Trump’s calumny that private texts between an FBI agent and lawyer critical of Trump reveal a Deep State conspiracy against the president. “When you have people that are in the highest echelons of the law enforcement of this nation saying things like that,” she said, “that sounds an awful lot like a coup and it could well be treason.” Only one problem: By revealing its investigation of Hillary Clinton but not of Trump, the FBI actually helped his 2016 campaign. But logic and facts are unnecessary encumbrances in the throes of partisan passion.

For pure, undiluted, 200-proof partisanship it is, as usual, nearly impossible to top Senate Majority Leader Mitch McConnell (R.-Ky.). He’s Exhibit C. On Tuesday, he was asked what he would do if there were a Supreme Court vacancy next year. “Oh, we’d fill it,” he gleefully said. Yes, this is the same senator who in 2016 refused to grant a vote to President Barack Obama’s nominee Merrick Garland, explaining, “The tradition has been that vacancies occurring in the Supreme Court in the middle of a contested presidential election are not filled.” Now McConnell is essentially admitting that no neutral principle can justify his conduct. His only principle is: Whatever helps the Republican Party is good; whatever hurts the Republican Party is bad.

Amash is the sole dissenter from this noxious orthodoxy. Other Republicans, such as Sens. Susan Collins (Maine), Mitt Romney (Utah) and Ben Sasse (Neb.), talk about being independent. Only Amash walks the walk. He is already paying a price for his heterodoxy: Trump has called him a “loser,” the wealthy DeVos family has cut him off and he has drawn two primary challengers.

This is exactly the kind of blowback that deters the 249 other congressional Republicans from calling out Trump for his criminal conduct, even though Amash says some of his colleagues privately agree with him. He alone remains undaunted. “We can’t let conduct like that go unchecked,” Amash said at a town hall on Tuesday. “Congress has a duty to keep the president in check.” He is right, and it is outrageous and infuriating that all the other Republicans refuse to do their duty.

A book on “Republican Profiles in Courage” would have only one chapter.

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