Alan Dershowitz, one of President Donald Trump's impeachment lawyers, presented an audacious new defense Wednesday during the president's Senate impeachment trial.

He said that if a president did something legal that he believed would get him reelected, and was therefore in the public interest, he shouldn't be impeached.

Critics say Dershowitz's arguments implied that President Richard Nixon should not have faced impeachment charges for covering up the Watergate break-in in 1974.

Nixon's allies had broken into the Watergate complex in 1972 to seek politically damaging information about the Democrats ahead of his reelection that year.

"Alan Dershowitz unimpeached Richard Nixon today," John Dean, who served as Nixon's White House counsel, tweeted Wednesday.

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Alan Dershowitz, one of the lawyers defending President Donald Trump at his impeachment trial, has based his defense not on a point-by-point rebuttal of the evidence presented by Democrats but on seeking to undermine the foundation of their argument.

Dershowitz has argued that abuse of power and obstruction of Congress — the charges on which Trump was impeached — aren't technically crimes and so can't be grounds for removing a president from office.

On Wednesday he took his arguments a step further, telling senators that presidents could not be impeached for legal actions they believed were in the public interest.

In other words, Dershowitz argued, because Trump believes his reelection is in the public interest, any legal actions he made to pursue that interest cannot be grounds for removal from office.

It is an argument that critics say evoked President Richard Nixon's infamous defense of total presidential authority in 1977: "When the President does it, that mean it's not illegal."

Nixon made this argument in an interview with the British journalist David Frost, three years after resigning from office while facing his own impeachment.

"Every public official that I know believes that his election is in the public interest," Dershowitz said Wednesday. "And mostly you're right. Your election is in the public interest."

"And if a president did something that he believes will help him get elected, in the public interest, that cannot be the kind of quid pro quo that results in impeachment."

It would therefore be in the public interest for Trump to leverage nearly $400 million in military aid to Ukraine while seeking investigations into his political rivals meant to aid in his reelection.

The argument neatly sidesteps the need to refute evidence that has emerged from the former White House national security adviser John Bolton, who in a coming book has reportedly claimed that Trump told him directly that he made Ukraine aid conditional on an investigation into former Vice President Joe Biden.

An image from video of Alan Dershowitz, an attorney for President Donald Trump, at the impeachment trial against Trump on Monday. Associated Press

'Alan Dershowitz unimpeached Richard Nixon today'

The Trump defense team's argument also has another huge ramification.

It blows up a decades-long consensus on the limits of presidential power and suggests that Nixon was right and did not deserve impeachment for his role in the Watergate break-in. It implies a startling expansion of presidential authority.

In 1974, Nixon was facing impeachment charges of abusing his power for covering up the infamous break-in at the Washington, DC, Watergate complex by his allies who were seeking politically damaging information about the Democrats ahead of his reelection.

He resigned from office before he could be impeached.

Nixon. US Government Photo

On Wednesday, John Dean, who served as White House counsel under Nixon, tweeted: "Alan Dershowitz unimpeached Richard Nixon today. All Nixon was doing was obstructing justice and abusing power because he thought he was the best person for the USA to be POTUS."

"Seriously, that was his motive! Agree with Alan and impeachment is gone!" he said.

Neal Katyal, a former US solicitor general, described Dershowitz's argument as "inane."

"That would allow a president to do literally anything and destroy re-elections as a check on presidential behavior," Katyal told NBC News. "I'm sure Nixon thought the break-in was OK because it aided his re-election, which was supposedly in the public interest, too."

In a subsequent tweet he added that if Dershowitz's arguments became policy, presidents would be less constrained in their use and abuse of power than monarchs.

Under Dershowitz's defense there is a caveat: A president guilty of a statutory crime can still be removed from office. But Nixon was never charged with any crimes, and Trump has not been either.

Regardless, the argument implies a staggering expansion of presidential authority.

Writing in The Washington Post, the former Democratic Rep. Elizabeth Holtzman, who sat on the House Judiciary Committee that voted to impeach Nixon in 1974, said Dershowitz was seeking to sweep the Nixon precedent "under the rug."

"I concluded from the Nixon impeachment precedent that, to constitute an impeachable offense, the president's misuse of the powers of his office must be grave and substantial, and must threaten our democracy," she wrote. "The articles of impeachment against Trump meet these standards."