Patrick will announce his campaign tomorrow in a video or online, one of the sources told POLITICO, and plans to visit New Hampshire on Thursday or Friday to file for the primary ballot.

His plans to leave Bain Capital, the private equity firm where he works, are "imminent," the source said.

“He’s in,” said a second source, who wasn’t authorized to disclose the information. “He’s under no illusions. It’s late. Money is a challenge. But it’s a big field and it’s wide open. No one is walking away with this and there’s space for his candidacy.”

“More candidates means more opportunity to with fewer votes,” the source added.

Patrick's presidential plans were first reported by CNN.

News that the former governor was considering a presidential campaign became public on Monday, and the final day to qualify for the New Hampshire primary ballot is Friday. Patrick will likely face an uphill battle in running for the nomination — the deadline to file for the ballot in two states, Alabama and Arkansas, have already passed.

It's unclear how Patrick's nascent campaign would affect the primary field. Patrick has the support of donors with ties to Wall Street, many of whom have doubts about former Vice President Joe Biden‘s staying power and worry about Sen. Elizabeth Warren, two of the leading Democrats in the race.

Patrick spoke with Biden earlier this week to tell him he was considering a run, according to a source with knowledge of the call. Warren, however, told reporters Wednesday that she had not spoken with Patrick.

“I’ve noticed that billionaires go on TV and cry. Other billionaires encourage their billionaire buddies to jump into the race. I believe that what our election should be about is grassroots," Warren said, when asked about Patrick and former New York City Mayor Michael Bloomberg, who is also considering entering the race.

Patrick considered entering the presidential race last year, but decided against it in December. Patrick‘s supporters saw him as having the right resumé to challenge Donald Trump — a candidate outside the fray of Washington politics, with a background in business but also a seasoned prosecutor, a mix of experiences that could blunt some Republican attacks. His relentlessly upbeat style and lofty rhetoric could serve as an antidote to some of the bitter divisions of the Trump era, they said.