Six GOP governors on Monday announced their endorsements of Sen. John McCain (R-Ariz.), whom Missisippi Gov. Haley Barbour described as “the man that can unite the Republican Party.”

Barbour and Georgia Gov. Sonny Perdue announced their support for McCain at a Washington hotel, where they also said fellow GOP Govs. John Hoeven (N.D.), Bobby Jindal (La.), Linda Lingle (Hawaii) and Bob Riley (Ala.) would support McCain.

Barbour and Perdue said their statement was not a call for former Arkansas Gov. Mike Huckabee, who won Georgia’s caucuses, to get out of the race. “Only he can make that decision,” Perdue said.

Huckabee also defeated McCain in Riley’s and Jindal’s states.

Barbour urged Republicans in states with upcoming Republican primaries, including Mississippi, which has a  primary slated for March 11, to vote and rally behind the Arizona senator.  Barbour said McCain will be the “clear choice” for both conservatives and moderates in November, since he will be facing a liberal Democrat. He also took shots at both Sens. Hillary Rodham Clinton (D-N.Y.) and Barack Obama (D-Ill.)

Obama is “the most liberal candidate for United States president in the history of our country,” according to Barbour.

He added, “I don’t have to convince anyone how liberal Sen. Clinton is.”

Asked if conservatives have come around to the Arizona senator, Barbour said, “John McCain is not as conservative as Haley Barbour is.” But he called the idea that McCain will not win conservative support in November “hugely unlikely” and “wishful thinking by the news media.”

Barbour also dismissed the possibility of a McCain-Barbour ticket. “I’m on hurricane duty,” said Barbour, whose state is still recovering from the effects of Hurricane Katrina.