A new poll shows Rep. Paul Ryan (R-Wis.) leading the field among possible GOP White House contenders in 2016. Here's why Republicans like him so much. (Casey Capachi/The Washington Post)

Last summer, Rep. Paul Ryan (R-Wis.) and Sen. Marco Rubio (R-Fla.) were paired in an ad campaign touting Rubio’s immigration legislation. Last week, they were on opposite sides of a cable news snit about the efficacy of a two-year budget deal co-authored by Ryan.

For those two young GOP princes, often hailed as the future of the Republican Party, a year of great ambition is ending in a muddle of unfinished business and disappointing compromises that might call both their futures into question.

Once atop every list of potential presidential contenders, Rubio and Ryan now find themselves looking up at a handful of Republican governors, ex-governors and outspoken tea party leaders in the 2016 sweepstakes.

And it seems that the cause of this diminished presidential stature can be traced directly to a single factor: the taint of Congress, the reviled institution in which they serve. Rubio, 42, and Ryan, 43, have spent the past months engaged in the ugly political process of legislative give and take. First, Rubio’s immigration effort, which passed the Senate and is now stuck in the House. And then Ryan’s compromise budget deal, which was approved 64 to 36 in the Senate on Wednesday but isn’t earning him any medals for aspiration.

Those legislative efforts represented the most substantive attempts by either lawmaker to try to bridge the party’s chasm between establishment conservatives and those who embrace the tea party’s confrontational style. Both were hailed by some of the party’s elder statesmen for doing the right thing, but both ended up on the receiving end of fierce criticism from conservatives.

Rubio is widely viewed as positioning himself for a 2016 run and is shying away from his leadership role on the immigration bill. Ryan appears more poised and confident than ever in the Capitol and seems noticeably more comfortable here than on the trail in early presidential primary states.

Ryan acknowledged as much this week. He told the Wall Street Journal that he intends to seek the chairmanship of the powerful Ways and Means Committee in 2015. At some point in 2015, he will decide whether to seek the presidency. But he acknowledged this week that his latest moves have done nothing to advance a presidential bid.

He said his budget deal was meant to help his party rather than boost his standing.

“If I was pining for myself, for what helps me in winning in Iowa or New Hampshire or whatever, I probably would have behaved differently, but I think that would have been unethical behavior,” Ryan told Milwaukee radio host Charlie Sykes on WTMJ.

On Tuesday, Rubio joined a group of 33 Republicans in a failed effort to filibuster the deal Ryan crafted with Sen. Patty Murray (D-Wash.), saying in a statement that the bill makes it “harder for more Americans to achieve the American Dream.”

It didn’t use to be this complicated for the two young Republican stars. Ryan, the budget committee chairman, has been viewed as his party’s brain, the policy wonk with the bold entitlement-overhaul plan. Rubio has been viewed as his party’s heart, the Cuban American with a personal Horatio Alger story and a soaring rhetorical style.

By the summer of 2012, Rubio and Ryan rose to the ranks of potential vice-presidential nominees. And although Mitt Romney selected Ryan as his running mate, he gave Rubio one of the most prominent speeches of the Republican National Convention.

The two are friendly with each other and, according to members of both camps, remain cordial despite their sharp differences on the budget deal. Ryan has been close friends with Rubio’s chief of staff, Cesar Conda, for two decades, dating to their work together at Empower America, the think tank founded by Ryan’s mentors, Jack Kemp and Bill Bennett.

Yet, the 2012 election framed the sometimes divergent paths each lawmaker took over the past year. As the results came in Election Day, Rubio became the most prominent Republican to call for expanding the party’s reach into minority and immigrant communities.

“Republicans need to work harder than ever to communicate our beliefs to them,” he wrote that night on his Facebook page.

By the end of January, Rubio had joined seven senators in a bipartisan framework for a comprehensive immigration and border security bill that would include a path to citizenship for the 11 million immigrants living in the United States illegally. He became its highest-profile salesman, doing six political shows Sunday. It won bipartisan Senate approval with 68 votes after he tirelessly appeared on conservative talk radio and TV shows.

Yet, doubtful tea party activists accused him of giving amnesty to law-breaking immigrants. Even one of his biggest patrons, former senator Jim DeMint (R-S.C.), told a Florida TV interviewer that Rubio’s popularity among conservatives had been “hurt some” because of the bill.

Ryan had a much quieter post-election time. First elected to Congress in 1998, Ryan had never before lost an election and had little time to absorb the loss, immediately returning to Washington for a pitched battle on the “fiscal cliff” legislation last December.

Then, as House Republicans feuded over the results of that divisive tax fight, Ryan worked behind the scenes to get enough GOP lawmakers to agree to suspend the debt ceiling for a few months to avoid having another epic fiscal showdown so soon after.

The move bought Republicans time to regroup, but just as importantly, it gave Ryan time. Time to think, time to reflect on the 2012 defeat, time to analyze his next steps.

“We were in a funk for a good six months,” he acknowledged in a speech last month in Iowa.

Ryan talked privately to a bipartisan group of House members trying to craft their own immigration bill. “We have to invite people to come out of the shadows,” he said in one immigration speech, aired by the U.S. Chamber of Commerce in a summer ad campaign.

But he never went all in the way Rubio did, never formally endorsed the comprehensive plan, and eventually the bipartisan group just withered away. House Speaker John A. Boehner (R-Ohio) has said he supports a piecemeal approach to immigration, a strategy that Ryan and Rubio now say they support.

Boehner has given no hint as to when such a step-by-step approach would begin.

Once immigration faded, Rubio threw himself in with tea party activists’ favorite senators, Ted Cruz (R-Tex.) and Mike Lee (R-Utah), who hatched a plan to force a government shutdown Oct. 1 to compel Democrats to accept a delay of Obama’s signature health-care law. Rubio joined them in Senate floor speeches, railing against other Republicans who were hesitant to take such an aggressive stand.

As the shutdown approached, however, Rubio moved into the background. Cruz became the political face of the 16-day standstill that left federal workers furloughed and national parks closed.

Once the shutdown ended, Ryan came out of his shell, having spent the summer touring inner cities as part of a burgeoning anti-poverty agenda. He pushed others aside to set up one-on-one talks with Murray to reach a budget deal that would virtually assure that the government would not shutdown again, avoiding another political debacle like the drubbing Republicans suffered in October. It wasn’t perfect, allowing for an additional $63 billion in federal spending in exchange for $85 billion in savings elsewhere.

DeMint’s Heritage Foundation, which has touted Ryan’s past budgets, blasted this deal for causing “unnecessary pain for Americans,” and Rubio issued his own condemnation of the deal as Ryan and Murray were publicly announcing it.

Late last week, Ryan grew restless from the criticism, particularly from Rubio, whose Senate Republicans have languished in the minority for seven straight years.

“In the minority, you don’t have the burden of governing, of getting things done,” Ryan said Thursday on MSNBC’s “Morning Joe.”

By Thursday night, Ryan won a major bipartisan victory, 332 to 94, with 70 percent of House Republicans supporting his plan. It was far less ambitious than his original budget outlines, but it might help his party in the upcoming elections, even if it chips away at his own chances at the White House some day.

“We’re going to have to win the Senate in 2014, and we’re going to have win 2016. If people like me have to jump on a political hand grenade every now and then, to make it better for us to actually win those elections, then I will die a happy man,” he told Sykes.