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.