Should an American president be able to solicit foreign interference in U.S. elections with impunity? It's a question that's near the center of Donald Trump's Ukraine scheme. It's a question that's been around for months. And it's a question Republicans still don't know how to answer.

On ABC News' This Week, George Stephanopoulos posed the question to Sen. Richard Shelby (R-Ala.), who said, "I don't know that has been actually proven. You know, that's all in dispute."

It's really not. We know this for certain in part because the White House released an official call summary of Trump's July 25 conversation with Ukrainian President Volodymyr Zelensky, in which the American president pressed his counterpart in Kyiv to "look into" Joe Biden. A week after that call summary was released to the public, Trump stood on the South Lawn of the White House and told reporters on camera, "China should start an investigation into the Bidens." The Republican added soon after, "I would say that President Zelensky, if it were me, I would recommend that they start an investigation into the Bidens."

Reminded of reality, Shelby suggested Trump's rhetoric didn't actually count, because it was "political." It led to this exchange:

STEPHANOPOULOS: So it's OK? SHELBY: I didn't say it was OK. I said people make them -- people do things. Things happen. STEPHANOPOULOS: Well, this is the president of the United States. SHELBY: Well, still the president of the United States is human. And he's going to make mistakes of judgment and everything else.

The senator added that he doesn't believe Trump's controversy "rises to the standard of an impeachable offense."

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It was a little painful to watch the Alabama Republican change direction so frequently, so quickly.

Shelby's first instinct was to falsely argue that the jury's still out on whether Trump sought foreign election assistance. He then quickly shifted, acknowledged that Trump did seek foreign election assistance, but suggested it wasn't important. The GOP lawmaker then shifted again, concluding that his party's president had made a "mistake," but not one he was inclined to care too much about.

All of this unfolded over the course of about 80 seconds.

What's more, it's worth appreciating Shelby's "things happen" declaration -- as if presidential extortion schemes are somehow routine incidents that American leaders occasionally stumble into -- which dovetails nicely with White House Chief of Staff Mick Mulvaney's "get over it" posture from October.

I mention this in part because it's generally amazing to watch the White House's GOP allies struggle while trying to cover for Trump's obvious misdeeds, and in part because Republicans have had several months to come up with an answer to the question about presidents soliciting foreign election assistance, and they still haven't quite figured it out.

This started in earnest months ago, when a few too many GOP lawmakers -- most notably Iowa's Joni Ernst and Colorado's Cory Gardner -- struggled mightily with the question, refusing to say much of anything.

In the months that followed, others in the party have tried to deny the existence of factual details altogether. Rep. Debbie Lesko (R-Ariz.), for example, was asked whether she believes it's all right for an American president to ask a foreign power to investigate a political rival. "He didn't," the congresswoman replied, reality be damned. "He didn't do that.... He did not do that."

Trump did exactly that. It's not one of the debatable aspects of the scandal.

All of which led to Richard Shelby giving it a try, weaving between talking points, culminating in a concession that Trump made a mistake about which the senator appears to be indifferent.

If Republicans can't think of a good answer, after months of planning, perhaps it's because the president's actions were, in a rather literal sense, indefensible.

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