The Senate voted on Friday to override President Donald Trump's veto on the defense spending bill in a rare New Year's Day session.

The stinging rebuke by members of Trump's own party represents the first time in his term that a veto has been overturned.

The vote was 81-13. A supermajority is needed to override a presidential veto.

Sen. Mitt Romney, R-Utah, confirmed today that Mitch McConnell, the Senate majority leader, called the upcoming joint session of Congress on Jan. 6, which will affirm the results of the presidential election, "the most consequential vote" of his lengthy tenure.

"I see that as a statement that he believes it's a -- it's a referendum on our democracy," Romney told reporters.

Sources said that McConnell asked Sen. Josh Hawley, R-Mo., on a New Year's Eve call with Republicans to explain to his colleagues why he is planning to object to the certification of Biden’s electoral win during the joint session. McConnell had privately warned his colleagues weeks ago against doing this as it would put his conference in the position of having to oppose Trump (and thereby his base) publicly.

Hawley, in joining the last-ditch bid by Trump's House allies to overturn the election results, said he objected to states not following their election laws.

"At the very least, Congress should investigate allegations of voter fraud and adopt measures to secure the integrity of our elections," Hawley said in a statement. There has been no evidence of widespread election fraud.

-ABC News' Trish Turner

In a very rare New Year’s Day session, Senate GOP leadership rejected two attempts to debate and vote on the House-passed CASH Act, which would give most Americans $2,000 in direct COVID relief payments. It was an effort by both Sens. Chuck Schumer and Bernie Sanders.

Republicans are continuing to argue that the House bill —- which would allow those making up to $350,000 to receive some cash under the act, albeit a smaller amount than those making less -- amounts to "socialism for the rich."

The chamber’s socialist, Sen. Sanders -- continued to argue that Republicans were “hypocrites” —- blocking this effort but approving big tax breaks for the rich.

He was joined by conservative Sen. Josh Hawley, who slammed the fight by his own leadership.

“With all due respect, this doesn’t seem to be Republicans against Democrats. This seems to be the Senate against United States of America,” said Hawley.

-ABC News' Trish Turner

The Senate is set to cast a preliminary vote this afternoon on overriding President Trump's veto of the National Defense Authorization Act -- which would be the first of his term.

The House voted overwhelmingly earlier this week to override Trump's veto of the $740 billion legislation, which funds the military and that members from both parties have said is vital to both the troops, who get a raise under the measure, and national security.

Trump has called the bill a "gift" to China and Russia.

In vetoing the measure (which has passed every year for 59 years), Trump demanded that Congress include a repeal of Section 230 of the Communications Decency Act, which gives broad legal immunity to tech companies over contents posted by users. He also wanted lawmakers to nix a provision authored by Sen. Elizabeth Warren that requires DOD to rename military bases and installations that honor Confederate generals.

Congress originally passed the measure with veto-proof majorities, and the House recently voted to override the veto. If the Senate votes to override - as it is expected to -- the bill would become law.

Today's test vote (which should be similar - if not identical - to the final vote) is expected to show more than the two-thirds majority required to override Trump's veto.

-ABC News' Trish Turner

Roger Stone told ABC News he saw Trump "in passing" Sunday night at the Trump International Golf Club in West Palm Beach, Florida, and thanked the president in person for pardoning him last week.

"My wife and I both had the opportunity to thank the president personally for righting the injustice of my conviction in a soviet-style show trial, which featured the epic bias of the judge who withheld exculpatory evidence from my defense, misconduct by the jury forewoman and substantial misconduct by the prosecutors," Stone told ABC News Monday.

"Donald Trump is the greatest president since Abraham Lincoln," he added.

Stone told ABC News he and his wife, Nydia Stone, were the guests of Newsmax publisher Christopher Ruddy for the club's buffet dinner, where they ran into Trump, who was dining with family.

"The president decided to dine at the club with his son Donald Trump Jr., Kimberley Guilfoil, Eric Trump and his wife Lara Trump. Because of his decision to sign the stimulus bill, it was unclear whether the president would dine at the club, which he normally does on Sunday nights when he is visiting Mar-A-Lago," Stone said.

The White House declined to comment to ABC News on the matter.

Because the club rules prohibit photographs of diners for privacy reasons, the Stones declined to provide a photo. However, ABC News reached a source who was present in a dining room of about 100 diners who provided a photo of Trump of greeting Stone with a pat on the shoulder.

Stone, a decades-long friend and former campaign adviser to Trump, was convicted on a seven-count indictment of obstructing justice, witness tampering and multiple counts of lying to Congress in special counsel Robert Mueller's investigation into Russian meddling in the 2016 presidential election in November 2019.

In July, days before the veteran GOP operative was scheduled to report to a federal penitentiary in Georgia, Trump commuted Stone's 40-month prison sentence.

Trump's full presidential pardon, issued Dec. 23, nullifies Stone's conviction entirely.

-ABC News' Ali Dukakis