Donald Trump
Donald Trump AFP

Donald Trump's trial on charges of covering up hush money payments to a porn star enters its closing stages Monday with the door still open to the former president taking the stand.

Most experts say it is highly unlikely he will testify in his watershed criminal trial, the first ever of a former US president, as it would expose him to unnecessary legal jeopardy and forensic cross-examination by prosecutors.

But on Thursday, Trump's lawyer Todd Blanche raised the prospect his client could step up as a witness, telling the judge "that's another decision we need to consider."

Before any testimony by Trump, defense lawyers will first conclude their grilling of the prosecution's star witness, Michael Cohen.

Cohen, Trump's former personal lawyer and fixer turned tormentor, recounted how he kept Trump informed about $130,000 paid to porn star Stormy Daniels to buy her silence about an alleged affair ahead of the 2016 presidential election.

Over several days of questioning, Trump's lawyers have set out to paint Cohen as a convicted criminal and a habitual liar, recalling his time in prison for tax fraud and lying to Congress.

Those arguments, among other grievances, have also been echoed outside the courthouse by an expanded entourage of Republican lawmakers, including House Speaker Mike Johnson, who have shown up to publicly back their party's leader.

Cohen has said repeatedly he takes "responsibility" for his actions and has faced the consequences. Prior to the trial, including in his books, he had done little to hide his contempt for his former boss.

Blanche has striven to ruffle Cohen, who has a reputation for a temper that could hurt him on the stand, but the witness has stayed largely composed and on topic.

His story has generally lined up with Daniels and David Pecker, the tabloid boss who said he worked with Trump and Cohen to suppress negative coverage during the Republican's 2016 White House run.

Trump meanwhile has complained his election campaign for another White House term is being stymied by the weeks-long court proceedings, which he has to attend every day.

Branding the case as politicized, he has been supported by a coterie of leading Republicans who stand behind him as he gives remarks to reporters outside the courtroom.

The growing list includes several lawmakers in the running to be Trump's vice presidential pick, such as Ohio Senator JD Vance and North Dakota Governor Doug Burgum.

Trump on Thursday again raged against "what a scam this whole thing is."

"I've been sitting here for almost four weeks. And we still have a long way to go," he said.

Trump, who appeared alert Thursday after spending some time over recent days with his eyes closed, denies he ever had sex with Daniels.

There was no hearing on Friday as Trump had been given the day off to attend his son Barron's high school graduation in Florida.

After the prosecution rests, the defense can present a case, with an election campaign finance expert the only confirmed defense witness for now.

But the prosecution has voiced opposition, saying that only the judge should explain how the law applies.

Trump famously considers himself his own best advocate -- but legal analysts believe he could be a liability on the stand.

When the jury begins deliberating, the often salacious testimony will likely linger front-of-mind -- but they will also have reams of documents to consider.

The charges hinge on financial records, and whether falsifying them was done with intent to sway the 2016 presidential vote.