But the subpoenas themselves — in conjunction with a series of other aggressive recent moves — show that Mayes, a Democrat, has cast a far wider net in her probe than previously understood.

Two people who were granted anonymity to discuss the sensitive probe described the Biggs subpoena. POLITICO reviewed a letter that Gosar sent to Speaker Mike Johnson on Feb. 16 disclosing his subpoena.

Spokespeople for Gosar, Johnson and Mayes declined to comment. A spokesperson for Biggs did not respond to multiple requests for comment.

Mayes appears to be nearing a decision on whether to ask the grand jury to issue indictments in the case. If she does, she will become the fourth state or local prosecutor to bring criminal charges over the efforts by Trump and his allies to submit fake electors in states that Joe Biden won.

In recent weeks, Mayes’ office has sent out a wave of grand jury subpoenas. She also has required Arizona Republicans who falsely claimed to be the state’s presidential electors to assert their Fifth Amendment rights in front of the grand jury — an unusual step that has generated criticism from some former prosecutors.

Biggs, the chairman of the conservative House Freedom Caucus in 2020 and 2021, and Gosar were among the most vocal congressional supporters of Trump’s efforts to overturn Biden’s victory in Arizona. Both tried to challenge the state’s presidential electors on Jan. 6, 2021, when Congress met to certify the results of the Electoral College. Gosar was mounting that challenge at the same moment a pro-Trump mob broke into the Capitol and halted proceedings.

Evidence gathered by congressional investigators showed that Gosar maintained relationships with activists organizing “Stop the Steal” protests targeting Congress’ Jan. 6 session.

Both lawmakers attended a White House meeting with Trump on Dec. 21, 2020, to strategize for how then-Vice President Mike Pence could block the certification of the election results, according to the Jan. 6 select committee.

According to text messages obtained by the Jan. 6 committee, Biggs quickly contacted Trump’s White House chief of staff, Mark Meadows, after Election Day 2020 to push for state legislatures to overrule the results in multiple states Biden won. Biggs also told Meadows that Trump should not concede the election and reportedly worked with other Arizona Republicans to advance the fake elector effort.

Arizona was one of seven states won by Biden where Trump’s allies organized slates of so-called alternate electors. Prosecutors in Georgia, Michigan and Nevada have brought criminal charges against false electors in those states, and special counsel Jack Smith has called the scheme a central element of Trump’s bid to subvert the election.

Subpoenas to members of Congress in criminal investigations are rare, in part because lawmakers enjoy robust constitutional protections from criminal proceedings connected to their official business. But Biggs and Gosar are not the first lawmakers to face scrutiny from criminal investigators probing Trump’s efforts to fight the 2020 election results.

In 2022, the FBI seized the phone of Rep. Scott Perry (R-Pa.) as part of the Justice Department’s election-subversion probe. A federal appeals court limited prosecutors’ ability to comb through many of Perry’s contacts with fellow lawmakers, particularly those squarely focused on their strategy related to certifying the election. Ultimately, prosecutors obtained access to about 1,600 of Perry’s emails, including contacts with the Trump White House and campaign.

Georgia prosecutors investigating the 2020 election aftermath also fought legal battles to compel testimony from Sen. Lindsey Graham (R-S.C.) and Rep. Jody Hice (R-Ga.). Graham’s fight reached the Supreme Court before he was ultimately forced to submit to limited questioning.

Details of Mayes’ probe have remained opaque, due in part to Arizona’s unusually strict — and, according to some experts, constitutionally dubious — state law banning witnesses from disclosing the fact that they have been subpoenaed.

“Getting a subpoena to testify in front of a grand jury is kind of rare,” said Jared Keenan, the legal director of the American Civil Liberties Union of Arizona. “And that’s why I think no one has challenged the secrecy law.”