Newcomers Challenge Leadership in the House WASHINGTON - Representative Justin Amash, a sophomore Republican from Michigan, is not one to mince words. For President Obama to strike Syria without seeking Congressional authorization, Mr. Amash warned on Twitter, would be "unquestionably unconstitutional and illegal." And when he mounted a challenge to the National Security Agency, over the objections of the leadership, that nearly passed the House this summer, Mr. Amash rallied his followers on Facebook, declaring ominously: "Have you talked to someone who has talked to someone who has talked to someone who has talked to someone who might be a terrorist? Well, the government might be spying on you. Mr. Amash, elected in the Tea Party wave in 2010, is part of a cadre of young, libertarian-leaning House members who have repeatedly hijacked their party's agenda, frustrating Republicans and Democrats alike. Their approach has prompted backlash, like when House Republicans stripped Mr. Amash, 33, and others of plum committee assignments after they repeatedly challenged the leadership. But now, armed with social media and a rigid set of beliefs, the self-styled revolutionaries in an already unmanageable Republican majority are making their presence felt - weighing in on issues like health care, government surveillance and Syria. "There's always a Justin Amash of every Congress," said Ari Fleischer, a press secretary to former President George W. Bush. It's an uncomfortable, difficult, healthy part of the Congressional process. At a lunch this summer sponsored by the Heritage Foundation, Representative Raúl R. Labrador, an Idaho Republican and fellow Tea Party conservative, said that he and Mr. Amash were part of a group he jokingly called "the Wing Nut Coalition - where you have the right wing and the left wing working together and trying to get things done." Mr. Amash, he added, was "chief Wing Nut." Mr. Amash rose to prominence in Michigan's Third Congressional District - filling a seat previously held by a mild-mannered Republican physicist - by capitalizing on a five-way Republican primary, which split the vote and allowed him to coast to his party's nomination with nearly 40 percent of the vote. Boyish looking with an easy grin and rimless glasses, Mr. Amash quickly became a nuisance in his own party's ranks, irritating the leadership and some of its more establishment members, who viewed him and his cohort as petulant and unwilling to compromise. He was one of four Republicans stripped of their committee assignments last year, and one of a dozen Republicans who did not vote to re-elect Representative John A. Boehner, Republican of Ohio, as the House speaker. "They never ever vote yes," a Republican familiar with the dynamics of the House said on the condition of anonymity for fear of offending a fellow Republican. There's always some more perfect thing that's completely impractical that they insist upon. They wind up pulling policy in the opposite direction from their stated goal, because if you are trying to pass something and you know they're going to vote no, you have to go to the left to pick up votes. Mr. Amash says that he is simply representing his constituents, and that he frequently votes with his party. Mr. Amash has broken with a majority of his Republican colleagues 27.5 percent of the time, the most of any House Republican. "We're filling a gap in leadership," Mr. Amash said. There have been a number of important issues that have come up where our constituents are asking us to take a position to present their perspective. Only midway through his second term in Congress, Mr. Amash is already considering a bid for Michigan's open Senate seat in 2014, though he is not expected to announce his decision until the fall. Liberty For All, a political action committee that supports candidates with libertarian principles, has already pledged "six figures" to support a Senate bid by Mr. Amash. Derek Willis contributed reporting. Earlier versions of this article misstated the home state of Representative Raúl R. Labrador. He is from Idaho, not Iowa.