"After talking with so many of you, and hearing your words of encouragement, I believe we are ready to move forward as a one, united team," Ryan said in a letter to colleagues. "And I am ready and eager to be our speaker."
The Wisconsin lawmaker and onetime GOP vice presidential nominee will be all but assured of triumphing in elections next week.
Ryan sought unity from divided Republicans as a condition for his candidacy. He succeeded in getting support from three major caucuses within the GOP, including the hardline Freedom Caucus that forced the current speaker, John Boehner, to announce his resignation.
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Paul Ryan is in, will seek job of House speaker
Speaker of the House Denis Hastert (L) administers the oath of office to Rep. Paul Ryan (R) of Wisconsin as his family looks on January 6, 1999 at the start of the 106th Congress. The oath is a recreation as the formal oath is administered to the entire congress as a body on the floor of the House. (photo by Rex Banner)
UNITED STATES - DECEMBER 12: Rep. Paul Ryan, R-Wis., speaks at a news conference in which House Republican leaders called for Permanent Tax Relief. (Photo By Tom Williams/Roll Call/Getty Images)
KRT US NEWS STORY SLUGGED: SOCIALSECURITY-DISCUSSION KRT PHOTOGRAPH BY GEORGE BRIDGES/KRT (April 14) Conversation on Social Security between Rep. Paul Ryan (R-WI), shown, and William Novelli, head of AARP, April 5, 2005 (lde) 2005 (Photo by George Bridges/MCT/MCT via Getty Images)
In this photo taken Dec. 1, 2015, House Speaker Paul Ryan of Wis. speaks on Capitol Hill in Washington.Talks on a massive, government-wide spending bill hit a snag Wednesday as Republicans pressed demands to block new power plant rules, weaken financial services regulations and make it more difficult for Syrian and Iraqi refugees to enter the U.S. (AP Photo/J. Scott Applewhite)
UNITED STATES - JULY 22: MEDICARE BRIEFING--Rep. Paul Ryan, R-Wisc., speaks at a Cato Institute briefing on Medicare reform in the Rayburn House Office Building. Tom Miller, director of Health Policy Studies at Cato, looks on. (Photo by Scott J. Ferrell/Congressional Quarterly/Getty Images)
WASHINGTON - SEPTEMBER 24: Rep. Paul Ryan (R-WI) questions Peter Orszag, director of the Congressional Budget Office, during a hearing on Capitol Hill about the impact of recent market turmoil on the federal budget on September 24, 2008 in Washington, DC. Orszag reported that while the impact is currently unknown, it is likely to be substantially less than $700 billion. (Photo by Brendan Hoffman/Getty Images)
WASHINGTON - APRIL 27: House Budget Committee ranking member Rep. Paul Ryan (R-WI) (R) delivers an opening statement during a conference committee meeting with Senate Budget Committee Chairman Kent Conrad (D-ND) (L) and House Budget Committee Chairman John Spratt (D-SC) in the U.S. Capitol April 27, 2009 in Washington, DC. House and Senate lawmakers have already struck a tentative deal on the FY2010 budget resolution and they hope to file a conference report after today's meeting. (Photo by Chip Somodevilla/Getty Images)
WASHINGTON - MARCH 19: (L-R) U.S. House Minority Whip Rep. Eric Cantor (R-VA), Rep. Dave Camp (R-MI) and Rep. Paul Ryan (R-WI) listen during a news conference on the health care legislation March 19, 2010 on Capitol Hill in Washington, DC. The House will vote on the Health Care Reform Legislation on Sunday, March 21. (Photo by Alex Wong/Getty Images)
Representative Paul Ryan, a Republican from Wisconsin and chairman of the House Budget Committee, speaks during a news conference at the U.S. Capitol in Washington, D.C., U.S., on Tuesday, April 5, 2011. U.S. House Republicans today unveiled a plan to overhaul the federal budget and slash the deficit in coming years by about three-quarters, with a $6-trillion cut in spending and 25 percent cap on tax rates. Photographer: Joshua Roberts/Bloomberg via Getty Images
MEET THE PRESS -- Pictured: Rep. Paul Ryan (R-WI) left, and moderator David Gregory, right, appear on 'Meet the Press' in Washington, D.C., Sunday, April 10, 2011. (Photo by William B. Plowman/NBC/NBCU Photo Bank via Getty Images)
MILWAUKEE, WI - APRIL 01: Republican Presidential candidate, former Massachusetts Gov. Mitt Romney (R) jokes with U.S. Rep Paul Ryan (C) (R-WI) during a pancake brunch at Bluemound Gardens on April 1, 2012 in Milwaukee, Wisconsin. With less than a week before the Wisconsin primary, Mitt Romney continues to campaign through the state. (Photo by Justin Sullivan/Getty Images)
WASHINGTON, DC - APRIL 26: House Budget Chairman Rep. Paul Ryan (R-WI) is introduced before speaking about 'America's Enduring Promise,' and the federal budget, in a speech at Georgetown University April 26, 2012 in Washington, DC. During his speech, Ryan said that his proposed budget confronts the nation's growing $15 trillion debt before it impacts future generations of Americans. (Photo by Win McNamee/Getty Images)
NORFOLK, VA - AUGUST 11: Republican presidential candidate, former Massachusetts Gov. Mitt Romney (L) jokes with Rep. Paul Ryan (R-WI) (R) after announcing him as the 'next PRESIDENT of the United States' during an event announcing him as his running mate in front of the USS Wisconsin August 11, 2012 in Norfolk, Virginia. Ryan, a seven term congressman, is Chairman of the House Budget Committee and provides a strong contrast to the Obama administration on fiscal policy. (Photo by Win McNamee/Getty Images)
UNITED STATES - SEPTEMBER 14: Rep. Paul Ryan, R-Wis., Vice Presidential candidate, waves to the crowd after addressing the Values Voter Summit at the Omni Shoreham Hotel in Woodley Park. Photo By Tom Williams/CQ Roll Call)
NEWPORT NEWS, VA - SEPTEMBER 18: Republican vice presidential candidate, U.S. Rep. Paul Ryan (R-WI), pauses as he speaks during a campaign rally at Christopher Newport University September 18, 2012 in Newport News, Virginia. Ryan continued to campaign for the upcoming presidential election. (Photo by Alex Wong/Getty Images)
MIAMI, FL - SEPTEMBER 22: Republican vice presidential candidate, U.S. Rep. Paul Ryan (R-WI) hugs waitress, Lourdes Alcerro, during a campaign stop at Versailles restaurant in the Little Havana neighborhood on September 22, 2012 in Miami, Florida. Ryan continues to campaign for votes across the country. (Photo by Joe Raedle/Getty Images)
Republican presidential candidate Mitt Romney (R) and running-mate Paul Ryan share a laugh as they are introduced at a campaign rally September 25, 2012 at Dayton International Airport in Vandalia, Ohio. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/GettyImages)
Representative Paul Ryan, a Republican from Wisconsin, arrives at a news conference on Capitol Hill in Washington, D.C., U.S., on Tuesday, Oct. 20, 2015. Ryan said he'd be willing to run for speaker of the U.S. House if Republicans unify behind him now, end leadership crises and let him continue spending time with his family. Photographer: Andrew Harrer/Bloomberg via Getty Images
Representative Paul Ryan, a Republican from Wisconsin and chairman of the House Ways and Means Committee, center right, walks down the steps of the U.S. Capitol building following a vote in Washington, D.C., U.S., on Friday, Oct. 9, 2015. Ryan is under heavy pressure from fellow Republicans to run for U.S. House speaker after a hard-line faction forced Speaker John Boehner to resign and his top lieutenant to drop out of the race. Photographer: Andrew Harrer/Bloomberg via Getty Images
Rep. Paul Ryan, R- Wis., leaves his office before a House GOP meeting, Tuesday, Oct. 20, 2015, on Capitol Hill in Washington. (AP Photo/Andrew Harnik)
Representative Paul Ryan, a Republican from Wisconsin, walks to a meeting in the basement of the U.S. Capitol in Washington, D.C., U.S., on Tuesday, Oct. 20, 2015. Ryan is set to meet with a group of House conservatives Tuesday as he weighs a potential run to replace Speaker John Boehner under pressure from fellow Republicans. Photographer: Andrew Harrer/Bloomberg via Getty Images
Rep. Paul Ryan, R- Wis. leaves his office before a House GOP meeting, Tuesday, Oct. 20, 2015, on Capitol Hill in Washington. (AP Photo/Andrew Harnik)
Representative Paul Ryan, a Republican from Wisconsin and chairman of the House Ways and Means Committee, center, talks to the media after walking out of the U.S. Capitol building following a vote in Washington, D.C., U.S., on Friday, Oct. 9, 2015. Ryan is under heavy pressure from fellow Republicans to run for U.S. House speaker after a hard-line faction forced Speaker John Boehner to resign and his top lieutenant to drop out of the race. Photographer: Andrew Harrer/Bloomberg via Getty Images
Rep. Paul Ryan, R- Wis. leaves his office before a House Republican meeting, Tuesday, Oct. 20, 2015, on Capitol Hill in Washington. (AP Photo/Andrew Harnik)
UNITED STATES - OCTOBER 20 - Rep. Paul Ryan, R-Wis., speaks at a news conference following a House Republican meeting, on Capitol Hill in Washington, Tuesday, Oct. 20, 2015. Ryan is stating that he will run for speaker only if he receives enough GOP support by the end of the week. (Photo By Al Drago/CQ Roll Call)
Rep. Paul Ryan, R-Wis., center, speaks to reporters on Capitol Hill in Washington, Wednesday, Oct. 21, 2015, following meetings with House Republican leaders and the Freedom Caucus members. Ryan seeking unity in a place it's rarely found, is telling House Republicans he will serve as their speaker only if they embrace him by week's end as their consensus candidate. (AP Photo/Manuel Balce Ceneta)
US Speaker of the House Paul Ryan, Republican of Wisconsin, awaits the arrival of Israeli President Reuven Rivlin for a meeting at the US Capitol in Washington, DC, December 10, 2015. AFP PHOTO / SAUL LOEB / AFP / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
WASHINGTON, DC - DECEMBER 10: House Speaker Paul Ryan (R-WI) holds his weekly press briefing on Capitol Hill on December 10, 2015 in Washington, D.C. Paul Ryan spoke on topics including Donald Trump and the spending bill. (Photo by Allison Shelley/Getty Images)
WASHINGTON, DC - DECEMBER 15: Speaker of the House Paul Ryan, (R-WI) speaks during a Politico interview at the Grand Hyatt on December 15, 2015 in Washington DC. Ryan was interviewed by Politico's Chief White House Correspondent Mike Allen during a Politico Playbook Breakfast. (Photo by Mark Wilson/Getty Images)
House Speaker Paul Ryan of Wis. welcomes Israeli President Reuven Rivlin on Capitol Hill in Washington, Thursday, Dec. 10, 2015. (AP Photo/J. Scott Applewhite)
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Ryan would inherit a House with major budgetary and spending deadlines on the horizon. At 45 he would become one of the youngest House speakers in history.
In announcing his potential candidacy for the speaker's job earlier this week, Ryan had said he wanted endorsements from all three groups to guarantee he would emerge as a unity candidate for House Republicans - not risk becoming the latest victim of the intraparty unrest roiling Capitol Hill and the presidential campaign. The Freedom Caucus' support fell short of a formal endorsement, since that would have required 80 percent agreement that the group was not able to achieve, but Ryan accepted it as a show of unity.
The decision would put the Wisconsin lawmaker in a role he never wanted and did not intend to seek, but could offer the fratricidal House GOP a chance to chart a new course after years of chaos, and allow Republicans to refocus away from fighting each other and onto the race for the White House.
"Paul's a uniquely capable communicator and it will be an asset for us to have his ability to frame the issues that we all care about," said GOP Rep. Patrick Meehan of Pennsylvania. Ryan's leadership will "support really what will be an agenda going into the 2016 campaign season," Meehan said.
Ryan had sought the speakership only when a dangerous leadership void emerged in the House after Boehner announced plans to resign under conservative pressure, and Majority Leader Kevin McCarthy abruptly withdrew from the race to replace him. Although a dozen or so other lawmakers were also exploring the race, most Republicans viewed Ryan as the only figure capable of uniting warring factions in the GOP.
Ryan initially demurred but relented under heavy pressure from GOP leaders - with conditions. He sought united support and enough flexibility to spend time with his wife and kids in Wisconsin. He also sought to change a House rule allowing an individual lawmaker to force a vote on ousting the speaker at any time, the arcane procedure conservatives were threatening against Boehner before he resigned.
That last point seemed to remain unresolved, since the Freedom Caucus specified that its support for Ryan didn't extend to the rules changes he sought. Indeed, members of the group suggested that their support for Ryan was just as conditional as his planned candidacy had been, and they could turn on him if he takes the House in a direction they don't want to go.
"We can support him and we want him to be successful, but we want to make sure also that he understands that this is not about crowning a king," said Rep. Raul Labrador of Idaho. "This is about working together and making sure that every member feels like they're empowered."
An early test may be the need to raise the federal government's borrowing limit by Nov. 3 or face unprecedented default. Most Republicans will not vote to raise the debt limit without concessions that the White House has already ruled out.
Another deadline looms in early December, on whether to pass spending legislation or risk a government shutdown.
Both instances might be cases where Republican leaders would have to rely largely on Democratic votes to achieve their goals, a practice the Freedom Caucus strongly opposes and wants to see Ryan avoid.