Budget deals bear hallmarks of how Ryan to govern as speaker

As for Ryan's ability to deal with the same pressures, Boehner said, "Listen, Paul knows how to do this." He pointed to the 2013 spending deal, which was forged two months after a 16-day government shutdown caused by a Republican effort to defund the Patient Protection and Affordable Care Act (PPACA).

"He knows the players and he has the respect of he players that make these decisions," Boehner said. "I don't think he'll have any problem at all."

Ryan agreed to run for speaker after locking up support from three major party groups last week, and Thursday's election will be just a formality. Yet those he needs to placate, especially members of the Freedom Caucus, have a long wish list.

They want to flatten the power structure and give more of a say to rank-and-file Republicans. Bills must go through committees in what's known as regular order, they contend, and should reach the floor only if most Republicans support them.

2012 run

Ryan's 2012 vice presidential bid with Mitt Romney made him one of the Republican Party's most visible figures and at 45, he stands to shape it for years to come.

"Unlike anybody I can remember in American history, millions of people have already voted for him," said Rep. Tom Cole, an Oklahoma Republican. "He's been on a presidential ballot so he's a known commodity which not a lot of people here are."

One thing that might come back to haunt Ryan is his promise to Freedom Caucus members to adhere to an informal Republican policy allowing legislation to reach the floor only if most party members support it. That would rule out, for example, the government funding bill passed Sept. 30 — with mostly Democratic votes — to avoid a shutdown the next day.

"That was the idea — that he would agree to do the will of the majority of the majority," said Rep. Morgan Griffith of Virginia, a Freedom Caucus member who described Ryan's promise to the group in a meeting last week. "It wasn't vague."

'Never a rule'

Boehner intended to follow that rule, too, when he took over as speaker in January 2011. In the end, a major factor in conservative dissatisfaction with Boehner was that sometimes he didn't follow the practice, relying on Democratic votes particularly when the government faced a possible shutdown or debt default. Ultimately, he said, it really "was never a rule to begin with."

Ryan's political trajectory has been upward in a Congress based on seniority. In college, he interned for U.S. Sen. Bob Kasten and spent time as a Capitol Hill staffer. Elected to the House in 1998 at age 28, this year he became the youngest chairman of the tax-writing Ways and Means Committee since 1861.

He forged a reputation as a no-nonsense legislator guarding against spending he deemed profligate. During four years as Budget Committee chairman, Ryan proposed repealing PPACA, cutting business tax rates, ending the estate tax and consolidating programs for low-income households. He sought to overhaul Medicare by giving future recipients a fixed amount of money to either buy private insurance or use in Medicare. Democrats say his plans would shred the social safety net.

He learned how to get results. In 2010, Ryan produced a comprehensive vision for changing U.S. fiscal policy called the Roadmap for America's Future.

See also: CBO: Ryan Proposal Would Cut Health Care Spending

It earned only 14 co-sponsors.

Budget chairman

The next year, after he became budget chairman, a similar plan passed the House by a 235-193 vote with only four Republicans in opposition. Ryan had tweaked the plan to leave out a proposal to privatize Social Security and conducted thorough information sessions with the entire Republican conference.

But there were departures from Republican orthodoxy: he voted for a bank bailout during the 2008 financial meltdown, and in September he backed a spending bill that didn't defund Planned Parenthood, as many Republicans wanted. He also has supported allowing 11 million undocumented immigrants to eventually become U.S. citizens, a stance backed by most Democrats but strongly opposed by most House Republicans.

In his 2014 book "The Way Forward: Renewing the American Idea," Ryan argued that the push to close the government in an unsuccessful effort to defund Obamacare — led by Texas Republican Senator Ted Cruz— wasn't a high-water mark.

"The shutdown wasn't a disagreement over principles, or even policies," Ryan wrote. "Rather, it is proof of what happens to a party when it's defined primarily by what it opposes, instead of by its ideas."

David Wasserman, who watches the House for the Washington-based Cook Political Report, said Ryan has to note Boehner's fate.

"By accepting responsibility to govern, Ryan is bound to disappoint at least some of his reluctant supporters," he said. "We're bound to have more of the same type of fights."

—With assistance from Erik Wasson and Sahil Kapur in Washington