WASHINGTON – The hostilities flaring between Mitt Romney and Gov. Rick Perry of Texas have been steadily rising inside both camps and may signal a new, more combative phase in the Republican presidential campaign.

The harsh exchanges between the men at a debate this week made clear the differences – in style and substance, background and belief – facing voters as they get closer to selecting the party's nominee.

But the animosities began long ago, set off by a series of political encounters that began when the two men were governors – Romney in Massachusetts – fighting over the services of a political consultant.

Romney's decision, as chairman of the Republican Governors Association in 2006, to hire a consultant who was working for one of Perry's political opponents left the Texas governor angry, aides said.

It was not long before Perry criticized Romney by name in his 2008 book about the history of the Boy Scouts. To Romney's annoyance, Perry noted that the Scouts were blocked from participation in the 2002 Winter Olympic Games, which Romney led.

"In the absence of an explanation," Perry wrote, "it is difficult to avoid the conclusion that the decision was made as a reaction to the protests of gay activist groups."

Romney beat Perry to the national stage, mounting his first bid for the presidency in 2008. Perry's decision to endorse Rudy Giuliani, the former New York mayor, over his fellow governor added to the insult that Romney felt, according to advisers.

Beyond personal slights, the ideological and personal gulf separating the pair – Romney, a wealthy businessman from Massachusetts whose father was a governor who also ran for president, and Perry, with his roots on a Texas farm – has added to the longstanding suspicion and ill will between them.

Romney declined to engage in a discussion about his rival Wednesday, but aides accused the Texas governor of acting like a bully at the debate.

"I don't think road rage is a quality people are looking for in their next president," said Stuart Stevens, a strategist for Romney.

It was Perry's testy, personal exchange at the debate in which he accused Romney of hiring illegal immigrants to tend his lawn at his Boston home that finally managed to rattle his seasoned opponent.

While Romney's advisers say they believe he fared better than Perry, his response may end up as a negative television ad.

"I'm running for office, for Pete's sake," Romney recalled telling the company that provided him lawn care. "I can't have illegals."

Asked whether Perry came across as too hostile in the debate, his communications director, Ray Sullivan said: "That's for others to decide. Governor Perry is a very competitive, passionate guy when it comes to his record and his conservative values."

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