Donald Trump raised a new legal argument on Thursday, and one legal expert has labelled the attempt "galling."

The former president is currently trying to delay the Supreme Court's consideration of his presidential immunity argument, which has him claiming that, as president at the time of Jan. 6, he should be exempt from any charges in connection with election subversion.

Earlier on Thursday, Trump filed a reply brief before the nation's highest court, which triggered a clock under which the Supreme Court could rule on the issue at "any time."

ALSO READ: Prison president: How Donald Trump could serve from behind bars

"Trump has replied to Jack Smith’s opposition to Trump’s stay motion. But his first argument is not that he meets any of the factors that must be established for a continued stay; it’s to accuse Jack Smith of partisanship," MSNBC legal analyst Lisa Rubin wrote. "In Trump’s portrayal, Smith’s sole reason to insist on a speedy trial would be to ruin Trump’s candidacy. What if the special counsel simply thinks Trump should be tried so that 1) voters have all the information; and 2) he cannot escape any trial at all through reelection?"

She then said it only goes downhill from there.

"But it gets worse—and even further afield from the actual legal questions at issue in Trump’s stay application. Trump is newly arguing the seven months Chutkan allotted for pretrial proceedings — a clock that would probably start again once the stay is over — is not enough," the ex-litigator added.

"And the why is galling," Rubin continued. "They trot out their usual 'there’s too much discovery!' complaint—but then argue Trump’s case will be impacted by an upcoming Supreme Court case on the proper interpretation of one of the statutes used to charge him."

"Cert was granted in that case on Dec. 13, 2023," she added. "Yet this is the first time Trump has made that argument; more significantly, the petitioner in that 1/6 case, Joseph Fischer, was not even present at the Capitol until 'well after Congress recessed'... And whether Fischer obstructed an official proceeding could be a vastly different question from the Trump case, in which his alleged obstruction did involve causing attempted evidence impairment."

Rubin is a legal correspondent for MSNBC and a former litigator. Prior to her current post, she was the off-air legal analyst for “The Rachel Maddow Show” and “Alex Wagner Tonight.”

The Supreme Court has sought to expedite review of Trump's immunity claim, which has already been rejected by a federal appeals court. "We cannot accept that the office of the Presidency places its former occupants above the law for all time thereafter," a three-judge panel ruled.

Trump then appealed the case to the Supreme Court. On Tuesday, Chief Justice John Roberts gave prosecutor Jack Smith until Feb. 20 to file his reply.