WASHINGTON (AP) — Alan Dershowitz delivered a stunning defense of President Donald Trump in the Senate that would essentially make it impossible to impeach a president for anything he might do to boost his reelection prospects. It was a contention quickly and forcefully denounced by a range of legal scholars and historians who said there were clear limits on presidential authority.

Dershowitz said on Thursday that his remarks have been misinterpreted, but Democrats seized on them as they pressed their case for Trump's removal from office for tying the release of military aid to Ukraine to an investigation of his political rivals.

His starting point was the benign assertion that every politician believes his election is in the public interest, but he pivoted abruptly to Ukraine, and began to frame an argument that would rewrite most conventional understanding of the scope of presidential power.

As novel as it was, his premise in many ways tracked the views of Trump who has said he was not bound by some constitutional constraints that other presidents have readily accepted. And several Republican senators seemed to find merit in what Dershowitz said.

The person in the chamber who in other settings might have a lot to say about the matter, Chief Justice John Roberts, was instead rendered essentially a spectator as he watched the arguments play out.

"If a president does something which he believes will help him get elected, in the public interest, that cannot be the kind of quid pro quo that results in impeachment," Dershowitz said Wednesday as senators put questions to Democratic House lawmakers who are prosecuting the case against Trump in the Senate and to Trump's defense team.

Robert Dallek, a presidential historian who has written books about five presidents, from Franklin D. Roosevelt to Ronald Reagan, called Dershowitz's argument unique. "Frankly I've never seen that before, that a president's power extends to wherever his politics are," Dallek said. "There is a pretty well defined idea of what a president can do and can't do and when he seems to overstep his bounds, he runs into great difficulty with the Congress or the judiciary."

Barbara Perry, director of presidential studies at the University of Virginia's Miller Center, said Dershowitz had it backwards in suggesting that the public interest is whatever serves the president's reelection campaign. "What we hope is that they at least think in terms of the nation's interests and then align their personal interest with the public interest, the country's interest," Perry said.

What's more, she said, Dershowitz's formulation could serve as a dangerous precedent for future presidents who might think they can do anything they want in the political arena, except for violation of a criminal statute. "Then there's nothing to be done about a president who can make the case that I did it in my self-interest," she said.

She reached back to Richard Nixon's presidency and the "dirty tricks" carried out to undermine the campaigns of Democratic rivals in 1972. "Nixon was trying to get reelected. Every single thing that happened in Watergate, all of those things would not be impeachable?" Perry said.

Both Perry and Dallek said the closest similar invocation of presidential power was Nixon's statement, made after he resigned the presidency: "Well, when the president does it … that means that it is not illegal," Nixon told interviewer David Frost in 1977.

Rep. Adam Schiff, D-Calif., alluded to Nixon in Thursday's Senate session. "We are right back to where we were a half century ago, and I would argue that we may be in a worse place, because this time, this time, that argument may succeed," Schiff said.

For his part, Dershowitz, a retired college professor, complained on Twitter that his argument was being "willfully distorted" by media outlets.

"They characterized my argument as if I had said that if a president believes that his re-election was in the national interest, he can do anything. I said nothing like that, as anyone who actually heard what I said can attest," Dershowitz wrote in a series of tweets.

"Let me be clear once again (as I was in the senate): a president seeking re-election cannot do anything he wants. He is not above the law. He cannot commit crimes. He cannot commit impeachable conduct.

"But a lawful act— holding up funds, sending troops to vote, braking a promise about Syria — does not become unlawful or impeachable if done with a mixed motive of both promoting the public interest and helping his RE-election. Please respond to my argument, not a distortion of it," Dershowitz wrote.