Wisconsin Gov. Scott Walker talks at his table before President Obama arrives to speak to members of the National Governors Association at the White House last month. (Carolyn Kaster/AP)

It started with a subtle poke at Jeb Bush almost two months ago, when Scott Walker suggested that Republicans need “a new, fresh approach.” Since then, Walker has continued jabbing, casting himself as the “son of a preacher” — instead of, say, a president — and warning Republicans against “looking to the past.”

With each provocation amid Walker’s fast rise, the Bush camp has grown increasingly agitated — not just by the attacks but also by what they see as a lack of scrutiny of the Wisconsin governor’s record.

Bush supporters fired back on Tuesday, starting when Al Cardenas, a Miami-based lawyer and longtime Bush supporter, took to Twitter to attack Walker’s shifting positions: “Did u know S Walker was for path to citizenship. Now not? Did u know he was against ethanol subsidy, now he is for? Do u really know him?”

In an e-mail to The Washington Post, Bush ally Ana Navarro repeated the theme, suggesting Walker was starting to sound a bit like that most renowned of Republican flip-floppers, Mitt Romney.

“Running for president requires having the mettle to keep your boots on, not change into flip-flops when it starts getting hot,” Navarro said in an e-mail. “I think the flip-flop label hasn’t yet stuck to Walker because unlike Romney, until now he’s had a low profile nationally.”

Jeb Bush and Scott Walker pose for a photo with the Sterling & Brass band in 2010 at a Walker fundraiser in Milwaukee (Courtesy of Jack Schulze//Sterling & Brass band)

The back-and-forth between the Republican camps is evidence of how the growing Bush-Walker rivalry has come to define the early stage of the 2016 GOP primary race, as well as how each presumptive candidate is planning to position himself against the other.

Walker wants to be the upstart outsider in the field, hoping to win over the grass roots as a fresh-faced conservative who stands apart from the old Washington ways. No one in the Republican field represents those ways more than Bush.

The former Florida governor, meanwhile, has fully embraced the establishment wing of his party and is raking in tens of millions of dollars from big-money donors. His emerging charge against Walker — voiced by aides and surrogates — is that the Wisconsin governor is not quite as conservative or consistent as he might seem.

Their upcoming travel schedules reflect the differences. When Bush shows up in New Hampshire on Friday, he will meet with the Greater Nashua Chamber of Commerce and attend a house party in Dover. He will also headline closed-door fundraisers for two GOP lawmakers on Friday and Saturday and meet privately with potential supporters.

Walker flies to New Hampshire for the first time as a potential candidate on Saturday and will appear at a state party training session for grass-roots Republican activists at a high school in Concord that is expected to draw more than 300 people, according to organizers. He will also meet privately with some supporters Saturday morning.

Jim Luther, a Walker backer and former New Hampshire state senator, said he and other Republicans have been grumbling about Bush’s plan to attend a fundraiser for Rep. Frank Guinta (R-N.H.) in which donors are being asked to pay $5,000 for access to what Luther called “the elite circle.”

“That’s Washington, D.C., pri­ces, and it really shows that this is the way Bush is carrying himself,” Luther said. “He has huge price tags. He’s not connecting. He’s a vacuum cleaner for dollar bills. But if you look at his policy points, he’s got a lot of work to do.”

American Bridge 21st Century released this video of Gov. Scott Walker (R-Wis.) speaking at an event in Nashville on Feb. 23. (American Bridge 21st Century via YouTube)

“I wish he’d listen to his mommy, who said we’ve had enough Bushes in the White House,” Luther added.

Bush and Walker’s political relationship began warmly five years ago this month when Bush gave Walker a crucial boost. He endorsed Walker, who was then the Milwaukee County executive, months ahead of the state GOP’s gubernatorial primary and headlined a $250-a-person fundraising event at the Pfister hotel in Milwaukee. A local brass band played at the cocktail reception, and Bush and Walker posed for a picture with the quintet.

In June 2012, shortly after Walker won a recall election, Bush told PBS’s Charlie Rose that Walker was “the real deal.” Days later, however, the first sign of tensions between the men appeared.

At a Bloomberg View gathering, Bush expressed that he had growing concerns about the modern GOP and its “orthodoxy that doesn’t allow for disagreement.” Appearing soon after at a breakfast hosted by the Christian Science Monitor, Walker told reporters he disagreed with the assessment by Bush, whom he called a friend who e-mails him “quite a bit on things out there.”

Since then, the two have been more cordial than chummy.

Last month at the Conservative Political Action Conference (CPAC), Walker touted his blue-collar roots, calling himself the “son of a small-town preacher” who did not have a chance to visit Independence Hall in Philadelphia until he was an adult. That was a double-knock on Bush, the son and brother of former presidents, who once chaired the National Constitution Center — down the street from Independence Hall.

Walker is also building a persona as a blue-collar newcomer online. In the lead video on the Web site for Our American Revival, Walker’s organizing group, the hush-voiced narrator warns Republicans to stop “looking to the past” over photos of working-class people with their heads in their hands.

The Bush camp is trying to stick the dreaded flip-flopper label on Walker over two issues: immigration and ethanol subsidies, the latter a closely watched issue in Iowa, where the nomination battle kicks off.

Walker once backed comprehensive immigration reform efforts but recently told Fox News: “My view has changed. I’m flat-out saying it.” And this past weekend at an agriculture conference in Iowa, Walker announced his full support for ethanol subsidies — a shift from his previous position, according to conservative news outlets.

In an e-mail, Cardenas said that his tweet was not sent on Bush’s behalf. But it nevertheless channeled the private frustrations of Bush aides who have bristled in recent days over their belief that Walker’s shifting positions have not been highlighted.

Cardenas is the co-chairman of a bipartisan task force on immigration reform that includes former secretary of state Condoleezza Rice and former Pennsylvania governor Ed Rendell (D).

“Walker was an ally when we started this journey,” Cardenas said. “I intend to call out anyone, not just him, who have changed their stripes on this issue to suit a presidential campaign run.”

Navarro added: “I’m a political junkie, and until very recently, I’ve been unfamiliar with his positions and record. I didn’t know he’d dramatically changed his rhetoric on issues like immigration and ethanol subsidies until I read about it. I think most Republicans are in the same boat as me.”

Bush is an advocate for comprehensive immigration reform and wrote a 304-page book on the subject. He also signaled tepid support for ethanol subsidies last weekend at the agriculture conference.

Bush has avoided directly criticizing his potential rivals. “I’m not going to tear down my fellow Republicans — that doesn’t help,” he said in Iowa this past weekend, echoing something he first told supporters at CPAC. “In order to get 50  [percent], you’ve got to be uniting the party rather than dividing the party.”