(CNN) -- If the recent CNN/Western Republican Presidential Debate in Las Vegas was any indication, the coming months on the campaign trail are likely to be nasty between Mitt Romney and Rick Perry.
After a shouting match between the two at the debate, Romney -- the former governor of Massachusetts -- responded, "Rick, again, Rick, again, I'm speaking. ... This has been a tough couple of debates for Rick, and I understand that. And so you're going to get testy."
While elections often bring out barbs and negative attacks, the animosity is real, observers say.
"Oh, they don't get along," said John Avlon, a CNN contributor, author and expert on independent voters. "They don't like each other."
"I mean, it (the debate dust-up) was amazing," he said. "You look at Rick Perry's eyes. I mean, this could have gotten physical if they were in high school." He added that while they have real philosophical differences, this time showed it was "personal animosity."
That point was backed up by Ed Rollins -- a longtime GOP strategist and former campaign manager to Republican candidate Michele Bachmann -- who said point-blank, "They don't get along" and predicted that this is going to be a "down and nasty race."
So is it just Perry's personality, or is there an anger management issue?
"He's combative, and people have asked me, 'Is Rick Perry mean?' and I guess the question is, which Rick Perry?" said Ken Herman, a columnist with the Austin American-Statesman in the Texas capital. "The Rick Perry I've known professionally and casually for 25 years? I wouldn't say he's mean."
Herman added that Perry, 61, is just tough, aggressive and a "cold-blooded politician."
William Murchison admitted in an article for the conservative magazine American Spectator that his friend's often "combative" style "may not prove as right for the moment as a style that says, calm down, I can fix this, give me a chance."
Perhaps it's that toughness, though, that has kept Perry in office for so long.
Perry holds the title as the nation's longest-serving governor and boasts that he's never lost an election since he first ran for the Texas House as a Democrat in 1984. He assumed his role as governor in 2000, when then-Gov. George W. Bush resigned to run for the White House.
Romney, meanwhile, has often been described as cool and calm -- almost robotic -- and takes a business approach to governing and rarely shows his anger, political observers say.
The former governor of the solidly blue state of Massachusetts has a history of crossing party lines to get legislation passed -- including the state's universal health care plan. Several of his rivals for the Republican Party nomination have criticized the plan, which they call Romneycare, for making all state residents get health care insurance through subsidies or mandates.
The dislike between Perry and Romney, though, comes down to their roots, Rollins said.
Perry was born and raised in Paint Creek, a small town in the western part of Texas, and is the son of a tenant farmer. He graduated from Texas A&M University and later joined the Air Force, where he flew C-130 aircraft. He later returned to Paint Creek to help run his parents' farm.
"He had nothing. He just scraped his entire life to get to where he was," Rollins said.
Perry is also deemed somewhat of a guys' guy, with a history of cowboy-like tendencies. In August 2010, he shot and killed a coyote while jogging with his dog in Austin. Perry said he often carries a pistol on the trails because of snakes and other wildlife.
Rollins said that perhaps Perry has anger for his fellow Republican because he "sees a guy like Romney who sort of had everything handed to him," referring to the fact that Romney, 64, is the son of George Romney, the former governor of Michigan who was once president of American Motors.
Romney took a much different path than Perry. Born in Detroit, he became a Mormon missionary and later graduated from Brigham Young University in 1971. Afterward, he received dual degrees from Harvard Law School and Harvard Business School. He later founded Bain Capital, a private equity firm, oversaw the 2002 Winter Olympics in Salt Lake City and successfully ran for governor.
He is worth an estimated $190 million to $250 million, according to 2011 documents released by his campaign. Perry, though, is also wealthy and has a proven track record of raising millions of dollars in campaign cash.