Former Vice President Mike Pence has been subpoenaed by the special counsel overseeing investigations into efforts by former President Donald Trump and his allies to overturn the results of the 2020 election, according to a person with direct knowledge of the event.

The subpoena to Pence as part of the investigation by special counsel Jack Smith was served in recent days, according to the person, who spoke to The Associated Press on condition of anonymity Thursday to discuss a sensitive issue.

The extraordinary scenario of a former vice president potentially testifying against his former boss in a criminal investigation comes as Pence considers launching a 2024 presidential bid against Trump. The two have been estranged since a mob of Trump's supporters stormed the U.S. Capitol building on Jan. 6, 2021, in an attempt to stop Democrat Joe Biden's victory.

ABC News first reported the subpoena.

Pence was at the center of Trump’s efforts to stay in power after losing the 2020 election. Trump falsely insisted that Pence, who had a ceremonial role in overseeing the certification of the election on Jan. 6, could simply reject the results and send the results “back to the States.”

That day, Trump supporters driven by the lie that the 2020 election was stolen marched to the Capitol building, brutally pushed past the police and smashed through the windows and doors while Pence was presiding over the certification of Biden’s victory. The vice president was steered to safety with his staff and family as some in the mob chanted, “Hang Mike Pence!”

Attorney General Merrick Garland tapped Smith, a former public corruption prosecutor, in November to serve as the special counsel for investigations into Trump’s attempts to subvert his defeat, his actions leading up to the Jan. 6 insurrection at the Capitol and his possession of classified documents after leaving office.

Federal prosecutors have been especially focused on a scheme by Trump allies to elevate fake presidential electors in key battleground states won by Biden as a way to subvert the vote, issuing subpoenas to multiple state Republican party chairs.

Federal prosecutors have brought multiple Trump administration officials before the grand jury for questioning, including former Trump White House counsel Pat Cipollone and Pence’s own former chief of staff, Marc Short.

In a sign of the expanding nature of the investigation, election officials in multiple states whose results were disputed by Trump have received subpoenas asking for communications with or involving Trump and his campaign aides.

A House committee investigating the Jan. 6 attack recommended that the Justice Department bring criminal charges against Trump and associates who helped him launch a pressure campaign to try to overturn his 2020 election loss.

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