But in recent years, Mr. Perry has broken politically with Mr. Bush, questioning his credentials as a fiscal conservative, accusing him of going on “a big-government binge” and playing down some of Mr. Bush’s accomplishments in Texas in light of his own.

Mr. Perry’s public statements exposed a long-simmering rivalry that had been little known outside the political fraternity here but underscores the rightward drift of the Republican Party since Mr. Bush was president. More acutely, Mr. Perry’s criticism holds potential peril and benefit for him should he decide to mount a presidential campaign, allowing him to establish an identity distinct from Mr. Bush but risking a guerrilla campaign against him by the former president’s inner circle.

Mr. Perry, who aides say will make a decision within weeks, has been meeting around the country with potential fund-raisers, went to Colorado last week for a gathering of prominent conservative rainmakers held by members of the Koch family, which helped finance the Tea Party movement. An inevitable question is whether Republicans will be willing to nominate another Texas governor so closely connected to the last one.

On government spending, immigration and education, Mr. Perry’s criticisms of Mr. Bush have given him cachet with conservatives, especially with Tea Party voters who blame the former president for allowing spending and the reach of government to grow rapidly.

Those criticisms have burnished the Perry image as less prone to ideological compromise or a fuzzy “compassionate” brand of conservatism, an appealing trait to those Republican primary voters seeking purity in their nominee. And they have helped Mr. Perry escape the shadow of Mr. Bush, whose sponsorship, along with that of his chief political strategist, Karl Rove, was critical to Mr. Perry’s rise.

But it antagonized Mr. Bush’s old team, many of whom endorsed Senator Kay Bailey Hutchison in her unsuccessful primary challenge to Mr. Perry last year. Some are indicating that they will oppose Mr. Perry should he join the presidential race with an anti-Bush message.

One close associate of the former president, speaking on the condition of anonymity to avoid a personal confrontation with the governor, warned Mr. Perry against establishing his own conservative bona fides by criticizing Mr. Bush, saying, “If you’re really trying to be the nominee and want to go the distance, you just don’t want the former president of the United States and his people working against you.”

Another, speaking anonymously as well, said, “He’s going to need all the help he can get from all the Republicans he can muster, so he ought to be prudent about that.”

The rivalry has become lore here in the state capital, at times bordering on urban legend. “An eight-foot alligator in the sewer,” said Mr. Perry’s chief political strategist, David Carney. Emphasizing that the two men were friends with more similarities than differences, Mr. Carney said, “They are in the same church, different pews.”

Neither Mr. Bush nor Mr. Perry would be interviewed for this article, and people close to both said the rivalry existed far more between their aides than between them personally.

The relationship between the camps includes a rich mix of political differences, class distinctions, loyalty questions and perceived slights of campaigns past. And it is a uniquely Texas story, opening in the Western dust bowl where both emerged — Mr. Perry as a conservative Democratic state lawmaker from a modest farming family and Mr. Bush as a failed Republican Congressional candidate of famous New England stock.

Mr. Bush had returned to his hometown, Midland, in 1975, to break into the oil business, after his years at Phillips Academy, Yale and Harvard Business School — time away from the state that Mr. Perry’s close associates brought up frequently in interviews. Mr. Perry returned to his struggling family farm in Paint Creek roughly two years later, after graduating from Texas A&M and serving as a captain in the Air Force.

Successfully running for the Texas House of Representatives in 1984, he won early attention as a dogged campaigner who flew himself to his own events in a beat-up propeller plane.

In 1989, Mr. Rove, already a powerful Texas political consultant, helped persuade Mr. Perry to join the Republican Party and run for agriculture commissioner.

Mr. Rove was heavily invested in Mr. Perry’s victory as lieutenant governor in 1998, and helped recruit Mr. Carney to run Mr. Perry’s campaign while he ran Mr. Bush’s. The tensions first spilled out publicly in 2007, when a video wound up on YouTube capturing Mr. Perry speaking dismissively of Mr. Bush http://www.youtube.com/watch?v=0EiLwrMuLEg at a Republican house party in Iowa for former Mayor Rudolph W. Giuliani of New York. In the video, Mr. Perry said, “George Bush was never a fiscal conservative — never was,” adding, “I mean, ’95, ’97, ’99, George Bush was spending money.”

Unhappy Bush aides noticed.

When Ms. Hutchison began running for governor last year, she had the backing of Mr. Rove and other Bush-world Texans including former Education Secretary Margaret Spellings, the presidential confidante Karen P. Hughes and former President George Bush and his wife, Barbara. George W. Bush’s associates said many former officials lined up with Ms. Hutchison before Mr. Perry said he would seek a third term — and after signaling that he had no plans to do so.

Other salvos followed. After initially embracing Mr. Bush’s signature education law, No Child Left Behind, Mr. Perry became a leading critic, calling it “a monstrous intrusion into our affairs” in an interview with National Review.

Ms. Spellings defended the law as offering more local control than it got credit for, adding, “There is a difference — and obviously this was true for candidate Bush when he became President Bush just as it would be true for a candidate Perry should he become President Perry — between campaign rhetoric and successfully enacting and passing and implementing legislation.”

Mr. Perry is said to believe that there is a big opening for a Republican like him in the race, and aides are mapping out how a campaign could come together. “The Republican field of candidates looks like a drought-stricken cotton crop,” said a close friend, Cliff Johnson.

Mr. Johnson served in the Bush and Perry state administrations, and the walls of his Austin office are adorned with pictures of both. Those of Mr. Bush — fresh-faced with brown hair — are a stark reminder of how the campaign and the job of president can age a person. That is among the factors said to be weighing on Mr. Perry, who is 61

Asked if Mr. Perry had reached out to Mr. Bush for advice, Mr. Carney said: “He’s going to make a number of calls. That will be one of them.”