President Donald Trump is running out of options to avoid possible impeachment or prevent his family from prosecution, legal experts say.

The felony convictions of two former top aides on Tuesday demonstrated that Trump's nonstop attacks have failed to impede Special Counsel Robert Mueller's Russia collusion and obstruction investigation against him.

And while no one knows how strong a case Mueller has built against the president and his inner circle, Trump's own behavior suggests he feels intense pressure.

Experts say he has three basic strategic options, none of them good.

Cooperate with Mueller

Though he repeatedly says there was no crime committed, Trump has tried disrupt and delay the investigation, and has avoided for months being interviewed by Mueller.

That's a bad strategy, if Trump truly has nothing to hide, says Eric Freedman, a constitutional law professor at Hofstra University.

"He should absolutely adopt and embrace a policy of openness," Freedman says, a move which could buttress the White House campaign to tarnish Mueller's probe as a political "witch hunt".

Doing so would require abandoning his support for former aides like Paul Manafort, Trump's ex-campaign chairman convicted on Tuesday on tax and bank fraud charges.

Trump could, however, justify that he is "draining the swamp" of Washington corruption, argues Freedman, "wrapping himself in the mantle of good governance."

Robert Bennett, a veteran Washington criminal defense lawyer who worked for president Bill Clinton in the 1990s, says it is too late for that.

"They decided a long time ago to attack the special counsel. It would be hard now to do an about-face," he told AFP. "Who is he going to turn on? He's at the top of the food chain."

Moreover, cooperating now would almost certainly not change the direction of Mueller's probe, except possibly for the worse, said Bennett, currently senior counsel at Schertler & Onorato, a Washington law firm.

An interview with Mueller would be fraught with dangers for Trump, who notoriously cannot stay on script. "He couldn't truthfully cooperate without further incriminating himself, is my guess," Bennett said.

Cooperating could also force the president into a difficult position if, as many think, his son Donald Trump Jr or other family members fall into Mueller's sights.

What then? "Stall as long as possible and pardon him," says Freedman.

Attack and buy time

Trump's immediate hurdle is the November 6 election, in which Democrats are threatening to take control of one or both houses of Congress. Trump needs to prevent that, to avoid having a Congress that would support impeaching him.

His current strategy has been to convince voters that Mueller's investigation is an illegitimate, pro-Democrat operation, in hopes of attracting support to Republicans. The effort appears to be having limited success, polls suggest.

In addition, the White House is demanding Mueller abide by a Justice Department policy for prosecutors not to take any action in the 60 days before an election that would impact any candidate.

Michael German, formerly an FBI agent and now at the Brennan Center for Justice, says the policy doesn't prevent Mueller from pushing ahead.

"Law enforcement doesn't stop every investigation 60 days before the election," German said. "I don't see anyone in the November election that has anything to do with those under investigation."

Bennett says stalling tactics worked when he defended Clinton against Paula Jones' sexual harassment charges. The case threatened Clinton's reelection chances in 1996, and Bennett forced a procedural issue to the slow-working Supreme Court to make the case disappear for months.

"My job was to get this Jones case out of daily media coverage," he recalled.

"We figured if we could get the Supreme Court to take the case, we were assured this thing would have less impact on the 1996 election. That's exactly what happened. Ultimately we lost in the Supreme Court but he won the election."

If Trump, or someone in his family facing charges, could get their case tied up in court over constitutional issues, it could take up to two years to resolve, to the end of Trump's term in office.

"No matter what the outcome, he'd probably be much better off," Bennett said.

The nuclear option

Trump could fire Mueller and shut down the investigation. He has repeatedly threatened to do so, but has held back under warnings from lawmakers that that could provoke impeachment.

The "nuclear option" didn't help president Richard Nixon when he fired Watergate special prosecutor Archibald Cox in October 1973. That further eroded support for Nixon, and Cox's replacement pursued the case anyway, until Nixon, nearly one year later, resigned in the face of certain impeachment.