LOS ANGELES, California (CNN) -- California Gov. Arnold Schwarzenegger announced Thursday he is endorsing Republican presidential candidate Sen. John McCain.
John McCain, right, looks on as Gov. Arnold Schwarzenegger announces his endorsement Thursday.
In endorsing McCain, Schwarzenegger lauded the Arizona senator's crusade against wasteful spending, his national security credentials and his environmental and economic stewardship.
Flanked by McCain and former New York Mayor Rudy Giuliani, who endorsed McCain on Wednesday, Schwarzenegger said he was giving McCain his blessing "because I am interested in a great future and I think Sen. McCain has proven over and over again that he is reaching across the aisle in order to get things done."
"He's a great American hero and an extraordinary leader," the governor said. Watch Schwarzenegger praise McCain »
Schwarzenegger made the announcement at a solar technologies company in Los Angeles, a day after the four Republican candidates debated at the Ronald Reagan Presidential Library in Simi Valley.
McCain is also set to receive the endorsements of Georgia's two Republican senators, Johnny Isakson and Saxby Chambliss, in the next two days, according to two GOP sources involved in the planning. McCain said during Thursday's news conference that Texas Gov. Rick Perry would endorse him later in the day.
California and Georgia are two of the 21 states holding GOP nominating contests on Super Tuesday next week. California boasts the most delegates and the most electoral votes in the nation.
Schwarzenegger's endorsement could be key to McCain winning California's delegates. Florida Gov. Charlie Crist's endorsement of the Arizona senator was cited in exit polls as a key to his winning there. McCain solidly beat former Massachusetts Gov. Mitt Romney and gained momentum with the win.
Momentum is essential in a race like this, especially in the GOP, and it could trump other factors, including campaign donations, said Dr. Christopher Hull, a Georgetown University adjunct professor and author of "Grassroots Rules," a book on the presidential primary process.
"The party will coalesce around the front-runner to defeat the insurgent candidate," Hull said. "It is a loyalist party at its roots."
California represents an enormous prize for McCain, not only because of the 170 Republican delegates, but also because of Schwarzenegger's support base.
Though observers aren't privy to the level of access, Schwarzenegger's endorsement could come with e-mail, mailers and phone calls encouraging the governor's supporters to get behind McCain.
"If McCain gets access to that organization, he gets a very strong tactical boost," Hull said.
Schwarzenegger has an impressive approval rating among California's self-declared Republicans, said Dr. Lynn Vavreck, an assistant professor of political science at UCLA. His popularity, along his fundraising ability, should represent a boon for the McCain, she said in an e-mail.
Vavreck added that McCain's endorsements are especially important among Republicans who have not yet chosen who they will vote for. Undecided voters often look to their party leaders for direction on how to cast their ballot.
"If voters were unsure about how to vote, their party leaders are not giving them signals about which candidate to rally around," Vavreck said. "All of [McCain's] endorsements reduce voters' uncertainty and ultimately help to coordinate their behavior."
On Wednesday, McCain got Giuliani's endorsement as the former mayor announced he was dropping out of the race.
"This is a man who is prepared to be president," Giuliani said of his "old friend."
Giuliani said McCain gives the Republican Party the best chance to hold onto the presidency. Giuliani made the announcement two hours before the Republican's final debate preceding the Super Tuesday contests next week.
Giuliani, who had staked his presidential campaign on a Florida win, had a disappointing third-place finish in the state's Republican primary Tuesday night.
McCain's Florida win essentially turns the GOP presidential race into a two-man contest between him and Romney. E-mail to a friend
CNN's John King and Eliott C. McLaughlin contributed to this report.
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