In recent weeks, some Democrats have struggled to cite a crime committed by President Trump in the Ukraine affair. While the Intelligence Community inspector general suggested the president might have violated campaign finance laws, Democrats have generally not specified what law or laws Trump might have broken — instead pointing out that, beyond treason and bribery, the Constitution does not list particular offenses that qualify for removal from office. The House has wide discretion in deciding what conduct, criminal or not, is impeachable.

Now, however, Democrats appear to be testing a new charge: The president committed extortion.

"We have a crime — extortion," Democratic Rep. Eric Swalwell told Fox News' Martha MacCallum Wednesday.

"You've already decided there was a crime?" asked MacCallum.

"Yes, that's why we're doing this," said Swalwell. "A crime was committed. We're now looking at the suspect, the president, who confessed to the crime, by the way."

The Democratic idea, apparently, is that Trump withheld U.S. military aid for Ukraine as part of a demand that Ukraine investigate the Bidens and events in Ukraine connected to the 2016 election. That is the alleged extortion to which Trump has "confessed," according to Swalwell.

Democrats encountered a problem with that theory early on in their investigation during an interview with Kurt Volker, the former U.S. special envoy to Ukraine. Rep. Adam Schiff, the Intelligence Committee chairman leading the Democratic impeachment effort, pushed Volker to say that the Ukrainians felt great pressure because Trump was withholding aid as he demanded an investigation.

Withholding the aid would give Trump "tremendous leverage" over Ukraine, Schiff said. "If it's inappropriate for a president to seek foreign help in a U.S. election, it would be doubly so if a president was doing that at a time when the United States was withholding military support from the country," he added.

Volker said the problem with Schiff's scenario was that events did not unfold as he said. During the time in question, Ukrainian officials did not know that the U.S. aid was being withheld, Volker said; they learned that in late August, while the notorious Trump phone conversation with Ukrainian President Volodymyr Zelensky was in late July. In addition, Volker explained, relations with the U.S. seemed to be good even though the Ukrainians did nothing that Trump mentioned in that call — no investigation and no public statement announcing an inquiry.

"To my knowledge, the news about a hold on security assistance did not get into Ukrainian government circles ... until the end of August," Volker testified. "And by the time that we had that, we had dropped the idea of even looking at a statement."

Still, Schiff insisted that Trump's call to Zelensky came in "the context of withholding foreign assistance." Volker said no, it did not.

"Congressman, this is why I'm trying to say the context is different, because at the time they learned that [aid was being withheld], if we assume it's August 29th, they had just had a visit from the national security advisor, John Bolton. That's a high-level meeting already. He was recommending and working on scheduling the visit of President Zelensky to Washington. We were also working on a bilateral meeting to take place in Warsaw on the margins of a commemoration on the beginning of World War II. And in that context, I think the Ukrainians felt like things are going the right direction, and they had not done anything on — they had not done anything on an investigation, they had not done anything on a statement, and things were ramping up in terms of their engagement with the administration. So I think they were actually feeling pretty good then."

Volker's comments came after an extended back-and-forth in which Schiff tried to get him to say that yes, the Ukrainians felt pressured. Volker never did; at one point, an apparently frustrated Schiff said, "Ambassador, you're making this much more complicated than it has to be."

The Schiff-Volker exchange makes more sense in light of a Democratic effort to show that President Trump committed extortion.

Extortion is a real crime and a word that is familiar to most Americans. People have actually been convicted of extortion. Contrast that to the alleged campaign finance violation some had discussed in relation to the Ukraine affair, in which the information gained from a Ukrainian investigation into the Bidens, if given to Trump, would be a "thing of value" and thus an illegal foreign campaign contribution. It was, to say the least, a stretch, and one that few Americans would likely understand.

But extortion is different. "We have a crime — extortion," said Swalwell.

"There was a concerted effort by this president and his White House to essentially extort the new president of Ukraine," said Democratic Rep. Gerry Connolly on CNN Wednesday.

"The president was attempting to extort the Ukrainian government," said Democratic Rep. John Garamendi on CNN Sunday. "The result of that extortion is, the president will be impeached."

The extortion charge has also popped up among commentators in recent days. In a sense, it is being test-marketed. Democrats do not need to cite a crime allegedly committed by the president in order to impeach him. But they do need to sell their case to the American people. And an accusation of extortion could help them do it.

