After a 45-minute delay, the House select committee has kicked off its second public hearing this month.

The committee today will focus on Trump's push of the "big lie" despite knowing he lost the election to Joe Biden. Last week, committee members began laying out their case against the former president, placing him in the center of what it described as an "attempted coup."

Bill Stepien's attorney Kevin Marino confirmed to reporters that Stepien planned to appear before the committee this morning but then learned his wife went into labor. Marino said it's his understanding that video testimony of Stepien from a previously taped deposition will be aired during the hearing.

Marino called Stepien "one of the finest political consultants in the country."

"You're going to hear that he followed the numbers, followed the data, and advised the president as to what he saw," Marino said.

Former Fox News political editor Chris Stirewalt, who was fired after defending the network's early projection that Trump had lost Arizona on election night, has written a blog post for The Dispatch, a right-leaning politics website, explaining why he agreed to testify before the Jan. 6 committee.

"I’m still not entirely sure what I will say or what may happen, and don’t want to close any doors or create any expectations. I had a pretty good perch for the 2020 election and was part of the best decision desk in the news business on election night," he said. "I’m still so proud of the work we did -- we beat the competition and stuck the landing. All I can do is tell the truth about my work and hope for the best."

Former Trump 2020 campaign manager Bill Stepien told the House select committee that his wife went into labor this morning, according to two sources briefed on the matter, explaining the family emergency that caused him to cancel his live appearance before the committee.

Stepien previously sat for a taped deposition before the committee, and vice-chair Liz Cheney told reporters to expect video excerpts of that deposition played Monday.

ABC News' Chief Washington Correspondent Jonathan Karl and Benjamin Siegel

Rep. Liz Cheney, R-Wyo., vice chair of the committee, told reporters to prepare for a substantial hearing despite Trump's former campaign manager Bill Stepien having to drop out from testifying live at the last minute due to a family emergency.

"We're going to have a very important and effective set of hearings. As you know, Mr. Stepien has appeared previously, and so we'll be able to provide the American people with a lot of interesting new and important information that Mr. Stephens provided to us previously," Cheney said.

She also confirmed the committee will show video of Stepien's interview.