Pagliuca sets his sights on Senate seat

Pagliuca’s team has worked over the past several days to develop the ads as he pondered whether to get into the race, those sources said. The ads will be up and running within days, they say.

His entry into the Democratic primary promises to have a major impact, given his ability to use his wealth - estimated at $400 million - to dominate the airwaves and build a formidable political operation. He will face Attorney General Martha Coakley, who is already in, and US Representative Michael Capuano of Somerville, who plans to make a formal announcement tomorrow.

Another potential Democratic candidate, Alan Khazei, the founder of City Year, is circulating nomination papers but has yet to declare his candidacy. His supporters yesterday posted a two-minute video on YouTube featuring mostly young voters and volunteers touting his potential candidacy. It was perhaps an early indication of how Khazei would run: as a grass-roots candidate from outside the establishment.

Advisers to Pagliuca yesterday would not discuss their plans or how much he expects to spend to try to win the Dec. 8 primary. One adviser said Pagliuca, a private equity investor and co-owner of the Boston Celtics, is ready to spend what it takes to make him a competitive candidate.

Will Keyser, a spokesman for Pagliuca, declined to comment on campaign strategy.

Pagliuca and partner Jack Connors, meanwhile, officially halted their effort to buy The Boston Globe, Connors said yesterday.

Pagliuca and Connors had submitted the lowest of the three bids on the newspaper, which called for the creation of a nonprofit foundation that would have had a stake in the newspaper.

The move means two teams of bidders remain: the California investment firm Platinum Equity and one led by Stephen Taylor, a member of the family that sold the Globe to The New York Times Co. in 1993 for $1.1 billion.

Connors, in an interview, said he supports Pagliuca’s Senate run and has no plans to pursue a purchase of the Globe on his own, or to join one of the other teams.

Pagliuca’s past support for Republicans - including his backing of Mitt Romney, a colleague from Bain Capital, in Romney’s 1994 challenge of Kennedy - is already causing friction in the race.

“The election is to determine who is best to carry on Ted Kennedy’s legacy,’’ Capuano said in an interview. “Does anyone think that the Massachusetts Democratic voters are going to elect someone to Ted Kennedy’s seat who opposed him and supported Mitt Romney? It is just not going to happen.’’

“If it happens,’’ he added, “I will be the most stunned politician in the world.’’

But Pagliuca’s advisers, who insisted on anonymity ahead of his announcement today at the TD Garden, said his support of Romney was based on their close professional relationship. They insist he is a progressive Democrat who embraces Kennedy’s political values and said he donated heavily to the Democrats and Barack Obama in last year’s presidential election.

Pagliuca, a Weston resident, had been a registered Republican up until 1998, when he enrolled as a Democrat. He supported William F. Weld in his 1996 race against Senator John F. Kerry.

Just days after Romney’s election as governor, in November 2002, Pagliuca donated $5,000 to the GOP State Committee. A week earlier he had given the state Democrats a $10,000 contribution.

Even as a Democrat, his voting record is spotty: He did not vote in the 2008 presidential primary, when Obama and Hillary Rodham Clinton were in a tight race.

Pagliuca grew up in a middle-class family in Framingham, attended Duke University, and received a master’s in business administration from Harvard Business School.

His central campaign theme is expected to center on his 20 years as a private equity investor, during which, those close to his campaign say, he has been on the front lines of the economic, financial, and health care issues facing the country.

Beth Healy of the Globe staff contributed to this report.