A woman demonstrates outside the Hart Senate Office Building on Capitol Hill during the Senate impeachment trial of President Donald Trump in Washington on Wednesday.

WASHINGTON — In a striking shift from President Donald Trump’s claims of “perfect” dealings with Ukraine, his defenders asserted Wednesday at his Senate trial that a trade of U.S. military aid for political favors — even if proven — could not be grounds for his impeachment.

Trump’s defense spotlighted retired professor Alan Dershowitz, a member of their team who said that every politician conflates his own interest with the public interest. Therefore, he declared, “it cannot be impeachable.”

The Republicans are still hoping to wind up the impeachment trial with a rapid acquittal. Democrats are pressing hard for the Senate to call more witnesses, especially Trump’s former national security adviser John Bolton, whose forthcoming book contends he personally heard Trump say he wanted military aid withheld from Ukraine until it agreed to investigate Joe Biden and his son, Hunter Biden.

Texas Republican Ted Cruz asked, Does it matter if there was a quid pro quo?

Simply, no, declared Dershowitz, who said that many politicians equate their reelection with the public good.

“That’s why it’s so dangerous to try to psychoanalyze a president,” he said.

Rep. Adam Schiff, the Democrat leading the House prosecutors, appeared stunned. “All quid pro quos are not the same,” he retorted. Some might be acceptable some not. “And you don’t need to be a mind reader to figure out which is which. For one thing, you can ask John Bolton.”

With voting on witnesses later this week, Democrats, amid the backdrop of protesters swarming the Capitol, are making a last-ditch push to sway Republicans to call Bolton and other witnesses to appear for testimony and ensure a “fair trial.”

Trump faces charges from the House that he abused his power, jeopardizing U.S.-Ukraine relations by using the military aid as leverage while the vulnerable ally battled Russia, and obstructed the House probe in a way that threatened the nation’s three-branch system of checks and balances.

The two days set aside for questions, Wednesday and Thursday, are allowing each side to grill the House Democrats prosecuting the case and the Republican president’s defense team.

Democratic Leader Chuck Schumer asked whether the Senate could really render a fair verdict without hearing from Bolton or acting White House Chief of Staff Mick Mulvaney, both potential eye witnesses to Trump’s actions. “Don’t wait for the book. Don’t wait ’til March 17, when it is in black and white to find out the answer to your question,” Schiff told the Senate.

That publication date is in doubt. The White House on Wednesday released a letter to Bolton’s attorney objecting to “significant amounts of classified information” in the manuscript. Bolton and his attorney have insisted the book does not contain any classified information.