Republicans in Congress have struggled to explain why President Trump’s phone call with the Ukrainian president is okay. Witness the top House Republican, Minority Leader Kevin McCarthy (R-Calif.), in an interview aired Sunday on CBS’s “60 Minutes.” Reporter Scott Pelley asks McCarthy whether what Trump has done is wrong.

McCarthy doesn’t directly answer the question. “You and I have all the information we need,” he says. “The president did nothing in this phone call that’s impeachable.” The exchange is instructive about how Republicans might move forward in this impeachment inquiry: switch the metric Trump is graded on from what’s wrong to what’s an impeachable offense.

This could be where Republicans’ hat will hang throughout this process: Maybe it was wrong (though McCarthy isn’t allowing that much), but it’s not impeachable.

That’s an easier argument for them to make because defining what’s impeachable is more subjective than describing what’s in a transcript that is out there for the world to see. The Constitution says a president can be impeached for “high crimes and misdemeanors,” but Congress determines what that means. There doesn’t have to be evidence of an actual crime. The framers defined “high crimes” in the sense of a crime of duty, a violation of the oath of office.

Democrats will argue that even by that vaguer definition, this is pretty cut and dried: Trump violated his oath to keep the United States safe by inviting foreign interference. But to the extent Republicans need wiggle room to accommodate a critical president whose base demands loyalty, this is it.

How they argue that Trump’s actions are not impeachable is their next challenge. They’ve struggled for a week to explain why the call is okay in a way that doesn’t dodge or misstate key facts about what was said. (At one point in his “60 Minutes” interview, McCarthy accused Pelley of adding a word in a key line of the transcript to make it more damning to Trump. Pelley had repeated the transcript accurately.)

The problem for McCarthy is that Republicans’ defense strategy of Trump thus far has been centered on casting doubt on the whistleblower. That slice of the strategy crumbles under the fact that we know what Trump did because his own White House released the rough transcript of his July call with the Ukrainian president. In it, Trump asks a foreign government to investigate one of his 2020 opponents. Republicans defending Trump have no way around the fact that to condone such behavior would be to condone foreign influence in an election.

Congressional Republicans in recent days have dismissed concerns about President Trump asking Ukraine to interfere in the 2020 election. (The Washington Post)

Others in the Republican Party describe the call this way: “It is a bad day and a bad week for this president and for this country if he is asking for political dirt on an opponent.” That’s Trump’s former homeland security adviser, Thomas Bossert, on Sunday on ABC’s “This Week.” He also said he was “deeply disturbed.”

“We have learned from a whistleblower that the president has abused the power of his office to pressure a foreign government to go after a political opponent,” writes former Republican senator Jeff Flake in an op-ed published Monday in The Washington Post. “A rough transcript of the telephone call has removed all ambiguity about the president’s intent.”

And he’s not a Republican anymore, but Rep. Justin Amash (I-Mich.) panned McCarthy’s performance defending the president as “dishonest."

The public opinion battle is far from over. A new CBS-YouGov poll shows a majority of Americans approve of the impeachment inquiry. But there is a section of the population that would seem open to hearing Republicans’ interpretations for why Trump shouldn’t be impeached. Thirty-one percent of Americans thought the call wasn’t proper but also wasn’t illegal, compared with the 41 percent who said it was illegal. (Twenty-eight percent thought the call was proper.)

There doesn’t have to be a crime for Congress to impeach a president, but it would stand to reason that those who think the president broke the law are more amenable to impeachment. So far, Republicans are struggling with how to articulate why they think Trump is in the clear.