Mitt Romney is moving quickly to reassemble his national political network, spending the weekend and Monday calling former aides, donors and other supporters — as well as onetime foes such as Newt Gingrich.

Romney’s message was that he is serious about making a 2016 presidential bid. He told one senior Republican he “almost certainly will” run in what would be his third campaign for the White House, this person said.

His aggressive outreach over the past three days indicates that Romney’s declaration of interest to a group of donors in New York Friday was more than the release of a trial balloon but rather was the start of a concerted push by the 2012 nominee to be an active participant in the 2016 campaign.

The news comes after rapidly increasing speculation that Romney would at least consider jumping into the race, including a Friday report that the Massachusetts Republican told a group of donors “I want to be president.”

Former Florida Gov. Jeb Bush has made the most aggressive move of possible 2016 contenders to-date, announcing the formation of a political action committee as part of exploring a bid. Just Monday, Romney’s former running mate, Rep. Paul Ryan, declared his intention to pass on a run and focus on his new role as chairman of the House Ways & Means Committee.