'I won't give in,' Cahill declares as he vows to stay in race

Patrick, meanwhile, came to Cahill's hometown this afternoon looking for new supporters in the Cahill stronghold. Patrick added a campaign stop at Darcy's Village Pub where he poured patrons' beers.

"I'm here in Quincy today today because I know there's a whole bunch of Cahill supporters here in Quincy," the governor said. "And I want them to know we want their support. We want them to be a part of this cause."

Earlier today. Baker took center stage to collect the surprise endorsement. Flanked by Loscocco and Tisei, Baker said the endorsement shows that Baker-Tisei ticket has a "ton of momentum'' behind it and that "people [are] realizing and recognizing that we are the best team to turn this state around.''

Loscocco was asked whether some of the criticisms he and Cahill have made of Baker in recent months are still valid today. "I don’t want to get into campaign rhetoric,'' he said.

Loscocco's sudden change of heart seemed to briefly confuse even him. At the press conference he told reporters at one point, "I am here to do whatever I can as part of Tim's team – excuse me, Charlie."

In a statement, Patrick campaign manager Sydney Asbury called the Loscocco move the "kind of political scheming is a distraction from the issues that truly matter in their lives, like job creation, education, and health care.''

Asbury added, "Today's news is just one more indication that Charlie Baker is a Beacon Hill insider who is more interested in the same back-room deals, and politics as usual that we have worked so hard to change.''

In a statement, John Walsh, the chairman of the Massachusetts Democratic Party, also lashed out at Baker, calling the endorsement a "back-room deal.''

"This October surprise will not fool voters,'' Walsh said in the statement. "Instead, this is a Halloween trick they will reject. Voters should also be asking what Mr. Loscocco is getting in return from the Baker campaign.”

At the press conference, Loscocco would not dismiss the possibility of working for a Baker administration. Loscocco is an attorney and former Republican state representative.

Loscocco's change of heart comes too late for the state to change the ballots voters will use in November, according to a spokesman for Secretary of State William Galvin.

Loscocco's name will be on the ballot, putting him in the rare position of being a candidate for public office who will not be voting for himself.

In a statement released prior to the press conference, Loscocco was quoted as saying that "I ran to have a spirited debate on the issues and to advocate for new ways to create jobs, lower taxes, protect personal freedoms, and fight for the principles of Ronald Reagan who inspired me to become a Republican as a young man.''

"The primary between the independent ticket and Republican ticket in the hearts and minds of the voters who want a change from Governor Patrick is now over. Charlie Baker and Richard Tisei have prevailed over Tim Cahill and me,'' Loscocco is quoted as saying.

Loscocco is a former Republican state representative from Holliston and was cochairman of John McCain's 2008 presidential campaign in Massachusetts. The Globe reported earlier this year that Loscocco helped lure McCain operatives to Cahill's campaign.

However, last week, John Weaver, a former chief operative for McCain, quit the Cahill campaign and endorsed Baker's candidacy.

“As much as I like Tim and believe he’d make a great governor, the choice does not now include him,'' Weaver told the Globe. "This is a race between Governor Patrick and Mr. [Charles] Baker, and I, and maybe others, can’t be a party to helping reelect the most liberal candidate.''

The following day, Cahill campaign manager Adam Meldrum resigned from the campaign.