WASHINGTON (AFP) - Texas Governor Rick Perry formally enters the 2012 White House race on Saturday, looking to supplant Mitt Romney as the frontrunner for the Republican nomination to take on President Barack Obama.

After months of campaigning in all but name, Perry was to make his candidacy official at events in the key early primary states of South Carolina and New Hampshire, joining a crowded field of Republican rivals.

"He's got to be considered a top-tier candidate. He immediately jumps to the top of the pack," Matt Dickinson, a professor of political science at elite Middlebury College in Vermont, said of Perry.

"The reason why Perry's a credible primary candidate ... is that he's from a state that created jobs in the recession," Dickinson told AFP.

Obama's most glaring vulnerability ahead of the November 6 vote remains the sour US economy, still grappling with unemployment above nine percent as it struggles to claw back from the 2008 global collapse.

Perry’s entry coincides with Saturday's straw poll in Iowa, another crucial early battleground where candidates such as Minnesota congresswoman Michele Bachmann and former Minnesota governor Tim Pawlenty are hoping for a strong showing to boost their chances.

Perry, who succeeded George W. Bush in the Texas governor's mansion in 2000, hopes to blend his strong credentials as an ardent social conservative and what his supporters call the economic "Texas miracle" into a winning political mix.

"I am a pro-business governor. I will be a pro-business president," Perry told Time magazine in an interview released Thursday, highlighting his opposition to taxes and regulation in tandem with his Christian faith.

Romney, a multimillionaire investor and former governor of Massachusetts, has been making the most of his private-sector experience on the stump, but faces lingering skepticism from core Republican voters for past moderate views on issues like health care and climate change.

Perry "poses a credible and a strong threat to Romney, because he (Perry) is in good standing with social conservatives," who regularly define Republican presidential primaries, said Dickinson.

The Texas governor has been nipping at Romney's heels in opinion polls of Republicans over the past few months, amid widespread discontent among party insiders with their crop of candidates.

And even before the announcement, Perry's Republican rivals and Obama's top reelection strategist, David Axelrod, were training their guns on the late-comer to the pitched political battle.

"If people want to send to Washington someone who spent their entire career in government, they can choose a lot of folks," Romney said at a Republican candidate debate in Iowa on Thursday.

"But if they want to choose somebody who understands how the private sector works, they're going to have to choose one of us, because we've been in it during our career," he said of himself and former pizza chain boss Herman Cain.

Cain shrugged at Perry's entry into the race, saying at Thursday's debate: "that's just one more politician, and that makes this business problem-solver stand out that much more."

While Romney's tack against Perry is "logical," said Dickinson, "voters are going to be less discerning. They don't care how jobs are created, they just want jobs."

The Texas governor has a reputation of a formidable fundraiser. According to The New York Times, in three campaigns for governor, he raised $102 million, including more than $39 million during his 2010 re-election bid.

"He is the most successful fund-raiser in the history of Texas politics," said Craig McDonald, director of Texans for Public Justice, told the newspaper. "He may be the best in the country."

Perhaps sensing the political danger, Axelrod told ABC television Friday that Perry had been the political "beneficiary of things that he had very little to do with" regarding his state's economic success.

"There's a specific reason that Texas has done so well, and that's because the oil industry has done so well in the last few years, and the military has grown because of the challenges that we have had overseas," he said.

Perry received 38 percent of the Latino vote in his most recent re-election victory, according to exit polling, and his recent prayer rally drew a large number of Latinos.

An ability to attract Latino votes, experts said, is likely to enhance Perry's appeal to those Republicans who say the party must improve its standing with the nation's fastest growing minority if it expects to flourish.