Sen. Mike Lee’s bold, outspoken conservatism isn’t sitting well with many of his more senior Republican colleagues in a chamber where even the staunchest of rivals tend to refer to each other as “my good friend.”

The freshman Utah Republican’s willingness to offer opinionated advice on policy and political strategy during closed-door Conference meetings has irked Members accustomed to Senate tradition, which values the input of tenured Members and expects the newly elected to maintain a deferential profile. Lee ousted Sen. Bob Bennett last year in a GOP primary, a factor that might have contributed to the tension.

“He’s not shy about sharing his thoughts. And in general, this is a place where the more you run your mouth, the more you irritate people,” a senior Republican Senate aide said. “He tends to talk very loudly and very authoritatively, not in a conversational way that invites discussion.”

Lee, in an interview with Roll Call, said he’s found the Senate to be collegial and declined to criticize fellow Republicans or the GOP leadership team over policy differences even as he displayed some of the confidence that has piqued some of the senior Conference members, including some in leadership. And the freshman Senator isn’t without his fans — on Capitol Hill and on K Street.

“One of the roles each Member of the caucus has, particularly a freshman Member, is to communicate things that we’ve newly discovered on the campaign trail,” Lee said Thursday. “We’re newly elected so sometimes we can share insights that we picked up. As freshmen, we had to spend a lot of time out on the campaign trail because we weren’t constantly flying back and forth to Washington to cast votes.”

Lee said he feels the “particularly big crop of freshman Republicans” are more willing to express what they hear outside Washington. And he insisted that expression is done “with respect to our more senior colleagues.”

But Lee’s critics describe the Senator as too influenced by conservative activist groups and as being more intent on attacking the shortcomings of Republicans than Democrats.

One Republican source who is familiar with the criticism that has been circulating about Lee described the Senator as “the new Jim DeMint.” The South Carolina Senator has taken heat from some Republicans over the years for his willingness to publicly criticize his GOP colleagues and oppose the National Republican Senatorial Committee in primaries. Those unhappy with Lee say it is mainly due to his style and actions in the Capitol.

Lee, 40, was elected last year as part of a generally more conservative class of Republican freshmen who won their seats on the strength of tea party support.

Lee and businessman Tim Bridgewater helped prevent Bennett from advancing to the statewide Republican primary ballot by holding him to third place in a vote of Utah GOP convention delegates — many of whom were tea party activists angry at the otherwise conservative sitting Senator for his vote in favor of the 2008 Wall Street bailout. Lee then defeated Bridgewater in the June 2010 statewide GOP primary.

Sen. Orrin Hatch is up for re-election for a seventh term in 2012, and some Republicans on and off Capitol Hill suspect Lee is working quietly to gin up GOP primary opposition to his fellow Utahan.

Even with Rep. Jason Chaffetz (R) opting against challenging Hatch at the convention, Lee has chosen to remain neutral in the primary. And, when President Barack Obama addressed a joint session of Congress on jobs in September, Lee gave his gallery ticket to state Sen. Dan Liljenquist, who Utah Republicans say is mulling whether to challenge Hatch in the primary. Hatch could be vulnerable, given the influence tea party activists have in Utah’s convention process.

Lee’s office disputes any suggestion that the junior Senator is working against Hatch. And the Senators say they have a good working relationship. But in the Senate, where egos are sensitive and Members’ reputations can be shaped by how they discuss an issue as much as by their positions, it’s easy to see how Lee giving a coveted ticket to a Liljenquist could be viewed as impolitic.

A Republican lobbyist with relationships on both sides of the aisle conceded that while Lee is likable, he was brash when he first arrived in the Senate in January. The lobbyist said that after nine months in the chamber, Lee is unlikely to “win a popularity contest.” But this lobbyist also praised Lee as among the most capable Republicans from the 2010 class and said he is personable and forthright.

“He didn’t come here to wait his turn in line. He came here with a mandate from the folks back home,” this Republican said. “He is a very effective, conservative-thought leader.”

Lee has forged connections with colleagues on the Judiciary Committee, including ranking member Chuck Grassley (R-Iowa), a Senate veteran who, over the course of his career, has displayed a penchant for bipartisanship. Lee also is close with other Republicans identified with the tea party, including Sen. Rand Paul (Ky.), who described the Utahan as “someone who helps me because he sees [legislation] from a lawyer’s point of view.”

Lee said he does not view himself as more impatient or vocal than any other freshman, while adding that he understands that his views on tactics and legislation will not always be adopted.

“I respect the fact that not everyone is always going to agree with me, either within the Conference or outside the Conference,” Lee said. “The fact that I disagree with a position leadership is taking might more accurately reflect the fact that I’m taking a position that differs from the majority of my Republican colleagues in the Senate.”