Washington DC - Former vice president Mike Pence testified Thursday to the grand jury investigating the January 6, 2021 Capitol attack in a major breakthrough for prosecutors probing ex-President Donald Trump.

Pence spent all day answering questions under oath for the first time about the former president’s effort to overturn the 2020 elections.

Just hours after an appeals court dismissed Trump’s long shot bid to block his testimony, Pence arrived at a Washington, DC federal courthouse around 8 AM and left around 4:30 PM.

Grand juries work in secret, and there was no immediate word on what questions Pence was asked or how he answered.

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Pence himself had agreed to abide by a separate ruling ordering him to testify about most but not all issues that special counsel Jack Smith may have planned to ask him about Trump’s efforts to overturn the 2020 election results.

Pence had never previously said under oath what he knows about Trump’s effort to overturn the election or what Trump may have told him behind closed doors.

Other witnesses have said Trump sought to bully Pence into backing his "Stop the Steal" campaign and hoped to get him to refuse to certify President Biden’s win at a January 6 congressional session.

Pence could shed light on Trump’s intent in pushing his election lies and delivering a fiery speech on January 6 when he urged his extremist supporters to "fight like hell" to keep him in power.

The then-VP was forced to flee for his life from rampaging attackers who stormed the Capitol and chanted "Hang Mike Pence!" He escaped to a secure area of the Capitol until security forces regained control of the compound hours later.

Pence, who is considering a run for president against Trump in 2024, has sought to avoid publicly criticizing Trump. He declined to appear before the congressional January 6 committee and fought a subpoena issued by the grand jury.