Rep. Kevin McCarthy (R-Calif.) enters a room full of leadership members before speaking to awaiting media at the Republican National Committee in September 2014. (Melina Mara/The Washington Post)

Rep. Kevin McCarthy (R-Calif.) finds himself at the doorstep of becoming the next speaker of the House after less than nine years in office, following Rep. John A. Boehner (R-Ohio), who announced Friday that he will resign from Congress next month.

If McCarthy does claim the speaker’s gavel, his climb to the top spot in the House will be the fastest since the 19th century. But his rapid ascent is grounded in a simple fact: In many ways, this is Kevin McCarthy’s GOP majority.

He did not amass nearly as much campaign money as Boehner, 65, or work the policy agenda as avidly as Eric Cantor (Va.), the ex-majority leader who McCarthy succeeded last year. But McCarthy has tended to this flock of House Republicans more than any GOP leader of the past five years.

He recruited many of the members to run in the 2010 elections that delivered the majority, he has been their adviser and confidant, he works out with them in the House gym and keeps tabs on family members.

“Kevin has really risen with the conference,” Cantor said Saturday in an interview, noting that his relatively brief tenure fits the narrative of a House Republican Conference dominated by lawmakers who have less than five years experience. “It’s about building the trust. Kevin’s had a very intensive training in that process.”

Washington Post reporter Aaron Blake explains what Speaker of the House John Boehner (R-Ohio) stepping down has to do with 2016 and which Republicans are on the short list to be the next speaker. (Sarah Parnass/The Washington Post)

However, the very reason for his success — his amiability and relationship savvy — is an issue that could return to haunt McCarthy should he succeed Boehner. The transition from a lower level post — just 15 months ago he was No. 3 in leadership — to becoming speaker is a sharp climb that will require more than just being the most likeable face at the leadership table.

He has never served as a committee chairman, nor does he have a major piece of legislation that defines his policy interests.

Some veteran lawmakers fear that the same group of conservatives that bedeviled the current speaker will trouble his successor. The next few months present several fiscal battles in which conservatives are pushing for a confrontation with Democrats in the Senate or a veto fight with President Obama. Democrats can slow or kill almost any legislation in the Senate where the threat of a filibuster requires 60 votes to move almost any legislation; there are 54 Republican senators.

“The next speaker is going to have to deal with those who deny basic math,” Rep. Charlie Dent (R-Pa.), a leader of the moderate wing, said. “It’s not just sad; there’s a sense of uncertainty and a little bit of a haze and a fog of not being sure where things are going to go.”

McCarthy has made no official declaration that he will try to succeed Boehner, but many rank-and-file Republicans have coalesced around the Californian as the next in line.

Many Republicans could be seen lining up to talk to McCarthy during votes Friday immediately after Boehner’s surprise announcement. Advisers said that he has spent his time taking and making phone calls to lawmakers to test their feelings.

The only rival so far is Rep. Daniel Webster (R-Fla.), a third-term lawmaker whose long-shot challenge to Boehner early this year secured 12 votes. Rep. Paul Ryan (R-Wis.), the only other Republican viewed to have enough personal gravitas to be speaker, all but endorsed McCarthy after Boehner dropped his bombshell on Friday.

House Majority Leader Kevin McCarthy (R-Calif.) and other GOP leaders speak to reporters after the weekly Republican Conference meeting in September 2014. (Melina Mara/The Washington Post)

Some committee chairmen, including Rep. Jeb Hensarling (R-Tex.), are taking the weekend to consider their options, including whether to launch bids for the No. 2 leadership post that McCarthy will likely vacate to become speaker.

The internal Republican election has not been set, but many expect it to come in less than two weeks to allow for the new speaker and his lieutenants to have a transition into their new jobs before Boehner’s Oct. 30 exit date.

A Speaker McCarthy would represent a sharp shift in the historical trends of the last 125 years. In that time, it took an average of almost 23 years in the House to be elevated to speaker, according to a Congressional Research Service report.

McCarthy’s mornings are spent in the House gym doing mixed martial-arts training led by Rep. Markwayne Mullin (R-Okla.), including Democrats such as Reps. Joe Kennedy (Mass.) and Tulsi Gabbard (Hawaii).

McCarthy’s political travels are not limited to the swing districts which determine the size of the majority; he will often do events for Republicans from the safest conservative districts just to get to know them.

McCarthy first met Rep. Trey Gowdy (R-S.C.), who is now running a special committee investigating the Benghazi attacks, during a 2010 campaign swing for Gowdy’s first congressional race, even though the newcomer was on his way to an easy win. The two are now close friends.

McCarthy also has had the sort of luck that politicians can only dream of, beginning with a winning lottery ticket decades ago that allowed him to start a deli in Bakersfield, in California’s lower Central Valley. He became a senior aide to the powerful local Republican congressman, Bill Thomas, who blended a deep knowledge of Congress with an acerbic demeanor.

Thomas retired in 2006 when his term was up as chairman of the Ways and Means Committee, and McCarthy coasted to victory to succeed his old boss. While most Republicans were despondent at having just lost the majority, McCarthy felt at home from his days in the Democratic-dominated legislature in California and quickly bonded with younger lawmakers such as Cantor and Ryan.

By 2009, Boehner let McCarthy lead the recruiting effort for the midterm elections, and McCarthy went out of his way to find eclectic candidates, not from central casting. When Stephen Lee Fincher, a gospel-singing farmer from west Tennessee, won his primary over more experienced Republicans, McCarthy spent the night dialing reporters to tout his favorite recruit.

Now five years later, Rep. Fincher is one of McCarthy’s closest allies.

As those elections approached, Boehner gave McCarthy the task of drafting the equivalent of a party platform.

“His ability to navigate it — putting together a document that represents the direction Republicans want to go in, in a way all of them could get behind — was the same kind of job he will be doing as speaker. His key decision was to make it about what we’re for, rather than including things we’re not going to do,” said David Winston, a Republican pollster close to Boehner.

Despite McCarthy’s famous geniality— he calls almost everyone “Sunshine” — he has sometimes had to be the disciplinarian, though he has not been as successful at the task as some veterans would like. As his party’s whip from 2011 to 2014, he suffered several embarrassing defeats because of the kind of conservative revolts that helped drive Boehner from office.

In one instance, McCarthy expelled Rep. Tom Graves (R-Ga.) from his whip team, but he did not give up on him. McCarthy continued talking to the conservative elected in 2010, working with him, and now he is considered trustworthy enough that he wields a subcommittee gavel on the Appropriations Committee.

Soon after Cantor’s loss, as McCarthy faced a nominal challenge to succeed his friend in the No. 2 post, he turned to none other than Graves to deliver a nominating speech at the closed-door elections. Graves, the onetime irritant to leadership, spoke of unity in promoting the fast-rising McCarthy another rung higher.

“We are one conference. We are one party. We are accountable for each other,” Graves said.

Robert Costa and Colby Itkowitz contributed to this report.