Sen. Jim DeMint’s (R-S.C.) speedy ascension to de facto leader of the Senate’s conservatives may have won him a number of fans among fiscal hawks, reform-minded watchdogs and some fellow Republican Senators, who applaud the first-term Senator for his willingness to buck the chamber’s “Old Boy” traditions. But DeMint’s tactics have started to chafe GOP leaders and prompted private warnings that their tolerance has worn thin.

DeMint led a small group of Republican conservatives who successfully killed immigration reform in June and has openly dueled with Democratic leaders over earmark reform, calling them out for refusing to adopt Senate-specific earmark rule changes before going to conference on a broader ethics bill that includes them.

That willingness to sidestep his leadership on immigration last month, and his ongoing fight with Majority Leader Harry Reid (D-Nev.) over earmarks reforms, has begun to irritate Republican Senate elders, including Minority Leader Mitch McConnell (Ky.) and Minority Whip Trent Lott (Miss.).

According to several Republicans, party leaders have made it clear to DeMint that while they may give him some running room over the next few appropriations-laden weeks, they will not tolerate what they see as repeated efforts to hijack the Senate floor and the public spotlight.

DeMint declined to comment directly on any warning leadership may have delivered to him regarding his increasingly high-profile crusades. But he did say it is up to McConnell and other GOP leaders to take up the mantle of reform if they do not want others to do so.

“I have a lot of respect for our leadership, and we work well as a team,” DeMint said. “But there are enough of us who believe this is where we need to go as a party. And we hope our leadership will take us there. But we’ll take up the banner if we need to.”

Publicly, many Senate Republicans applauded DeMint’s courage to take on the normally decorous chamber and for sticking up for conservative principles at a time when the party is struggling to regain its footing. But several Senators and high-level aides also privately noted that DeMint needs to be careful not to go too far, with several saying he runs the risk of being marginalized as he carves out a reputation of a flame-throwing, first-term Senator who casts aside legislating altogether.

“You have to always be careful around here not to overplay your hand,” Lott warned last week.

Although disagreements between the two date back to DeMint’s opposition to a Lott proposal to move train tracks in his state following Hurricane Katrina, the two have had an ugly split in recent weeks over DeMint’s role as Republican Steering Committee chairman. According to GOP aides, Lott yanked his annual $7,500 contribution to the committee’s funding after DeMint aides criticized his efforts to push through the failed immigration reform bill. Lott’s move to pull the funds was first reported in Congressional Quarterly.

“At some point [DeMint is] going to have to learn he can’t always throw missiles,” said one senior Republican aide. “He’s going to have to work on diplomacy. But so far he’s been rewarded for his behavior and has yet to pay a price for it.”

With that in mind, Republican sources said GOP leaders are keeping a close eye on the South Carolinian as he continues his crusades. Those GOP sources said conversations between the leadership and DeMint have taken place, and the message has been made clear that McConnell’s patience isn’t limitless when it comes to DeMint’s efforts to block legislation or shut down the chamber to push his priorities.

So far, however, most of DeMint’s colleagues — especially those in conservative corners — seem to be accepting of his procedural maneuvers.

“My own view is it’s every Senator’s right to protect their interests,” said Sen. Judd Gregg (R-N.H.). “He was very effective on the immigration bill, and a lot of his colleagues were with him.”

And while Gregg acknowledged DeMint carries less favor with Senators over his current cause to use the ethics package as the vehicle for his opposition to earmark spending, he believes DeMint’s standing in the Conference remains intact.

“Everyone is very individualistic around here,” Gregg said. “You don’t run the risk of losing the respect of your colleagues just for being individualistic. It’s just the opposite.”

But not all Senators view it that way, especially among veteran Republicans who cherish a chamber that’s known for putting a premium on decorum, deliberation and seniority. DeMint, in contrast, was part of the more aggressive band of Republicans elected in 1994, some of whom have since moved from the more partisan House to the Senate.

Sen. John Ensign (Nev.), who as chairman of the National Republican Senatorial Committee is in the leadership circle, said the reviews of DeMint’s tactics “depends on what side you are on.”

For Ensign, that’s on the side of DeMint and others who he called “a breath of fresh air in the U.S. Senate.” Still, Ensign conceded that the approach isn’t without flaw, saying: “There’s always a risk, there’s always a balance. But when you are in the minority, you need to exercise your rights.”

Indeed, DeMint has a loyal following among more junior Republicans, particularly his fellow House alumni, and those Senators who believe it behooves the party to fight rather than negotiate with the now-majority Democrats.

“It’s a thankless task,” said Sen. Jeff Sessions (R-Ala.), who joined DeMint in his efforts to defeat the immigration reform measure.

“Some people get mad at him, they want him slowed down,” Sessions said. “But right now, most Republicans respect what he’s doing. Really, my impression is that even those who are dubious of DeMint’s leadership are beginning to feel like this is healthy and that maybe we do need a more vigorous debate.”

DeMint said while some senior Republicans such as Sen. Kit Bond (Mo.) have supported him, he acknowledged that much of his backing has come from the GOP’s increasing ranks of junior lawmakers.

“It’s not universally true, but to a point it’s true. It’s one of the unfortunate things that has happened to Congress over the years,” DeMint said, adding that many lawmakers are afraid to speak out because they are afraid of reprisals.

“A lot of people are afraid if they come out strong against earmarks they’re not going to get any,” DeMint noted.

As for the chamber’s more entrenched Members, DeMint argues that their opposition — both public and private — is motivated by their desire to keep cash flowing to their states. “A lot of their power and clout back home is based on how much money they can bring home,” he argued.

DeMint said his party would be wise to take up the issue of ethics as a central fight, arguing that in recent weeks he has seen increasing interest across the country in his battle with Reid. “In some ways this is immigration all over again in that out in the public there’s a feeling that this is wasteful spending” and that Congress is failing to seriously address the issue, he said.

DeMint also has begun to reach out to the vast network of editorialists and talk radio hosts that backed his successful rebellion against the immigration debate and has been credited with giving DeMint and his supporters enough public support to defeat the bill.

Significantly, he also has begun to see support from other media outlets, which are not normally connected to the conservative world. For instance, the Los Angeles Times editorial board has come out in support of his work, DeMint noted, and he believes that people across the country are becoming increasingly upset with Congress’ handling of earmark reform.

DeMint — who calls the earmark process “one of the corrupting [forces] of Washington” — said McConnell has so far backed his efforts to force Reid to accept the Senate rule changes before conference to ensure no changes to the earmark reforms are made. “Mitch McConnell is very supportive of what I’ve been doing,” DeMint said, adding that “he’s asked me to work with Sen. Reid” to find a solution.

But Reid “has been stonewalling me,” DeMint said, and seemed skeptical that any solution appears imminent.

DeMint also said that regardless of his leadership’s complaints or demands — or those of the Senate’s old guard — he will not back down. “This isn’t a job I wanted, but I’m good at it,” he said, adding, “I’m going to continue doing what I’m doing.”