Here are six examples from the Iowa Freedom Summit:
1. Trump vs. Romney/Bush:
Donald Trump was clear with his fire:
"It can't be Mitt, because Mitt ran and failed. He failed," Trump said to cheers from the audience. "He choked. He had that election won."
He was just as clear when it came to Bush:
"You can't have Bush," Trump said, criticizing the former Florida governor's support for Common Core education standards and immigration views, as well as his brother former President George W. Bush. "The last thing we need is another Bush."
2. Walker vs. Possible Rivals
He also described in detail how thrifty he and his wife are telling the crowd that next month he will celebrate his 23rd wedding anniversary with his wife Tonette, but when they were first married he "made a critical mistake."
"I went to a Kohl's department store and I bought something for the price it was marked at," Walker said. "My wife said to me, 'You can never go back there ever again until you learn how to shop at Kohl's.'"
He then detailed his frugal shopping skills, saying he could get so much money off the price of a shirt, "the next thing you know they are paying me to buy that shirt."
The crowd cheered his budget-cutting ways, and although he didn't mention any of his possible Republican rivals by name he set up quite contrast with at least two of his wealthy possible opponents, Jeb Bush and Mitt Romney. Expect to hear this all again if they do get on the campaign trail.
3. Gilmore vs. Christie/Bush/Romney
Former Virginia Gov. Jim Gilmore went after both Bush and Romney without mentioning them by name, attacking Bush for his support of Common Core education standards and then asking the crowd, "Do we want a nominee who enacted state control of health care and then flipped and said he was against Obamacare?" The audience yelled, "No" in response. Gilmore was referring to Romney's health care plan in Massachusetts, sometimes referred to as Romneycare.
4. Santorum vs. Paul
"We have seen the impact of isolationism, we have seen the impact of weakness and indecision on the part of an American president, an inexperienced, raw American president who had ideologies that didn't face reality," Santorum said. "Ladies and gentleman, in this election cycle, we need to be looking for somebody who has that experience, who's been tested and understands. I spent 16 years in the House and Senate, eight of those in the Senate Armed Services committee."
Santorum has previously criticized Paul on his foreign policy, calling him an isolationist, something Paul regularly denies.
5. Palin vs. The Establishment
She told the crowd the "GOP primary" should be a "competition, not a coronation."
6. O'Brien vs. Romney/Bush
Bill O' Brien, the former speaker of the New Hampshire House of Representatives, didn't mention Romney and Bush by name, but he also could not have been clearer when he told the audience, "We lose when we nominate RINOS," or Republicans in Name Only.
"What is worse, nominating someone merely because he's been nominated twice before or nominating a liberal supporter of Common Core because he has a familiar name," O'Brien said