NORFOLK, Va. — Republican presidential candidate Mitt Romney has picked Wisconsin congressman Paul Ryan to be his running mate, according to a Republican with knowledge of the development. They will appear together Saturday in Norfolk, Va., at the start of a four-state bus tour to introduce the newly minted GOP ticket to the nation.

The official spoke to The Associated Press on condition of anonymity because this person was not authorized to disclose the decision.

In a statement issued Friday night, Romney’s campaign would say only that the running mate would be revealed at 9 a.m. EDT at the Nauticus Museum. Berthed at the museum is the USS Wisconsin — which offered a hint about Romney’s choice.

Before Romney’s team issued the statement, all signs seemed to point to Ryan, the seven-term Wisconsin congressman whose nomination could help assuage the conservative base of the party that has been reluctant to fully embrace Romney.

Romney’s preference for a team player cannot be overstated in a campaign led by an inner circle that has worked together for a decade in some cases.

Campaigning together during this spring’s GOP primary, Romney and Ryan were visibly comfortable with each other on a personal and professional level. Romney eagerly shared the microphone with Ryan during campaign events, they shared hamburgers at a fast food restaurant, and the congressman played a leading role in an April Fool’s joke on the Republican presidential contender.

In recent days, conservative pundits have been urging Romney to choose Ryan in large part because of his authorship of a House-backed budget plan that seeks to curb overall entitlement spending and changes Medicaid into a voucher-like system to save costs.

On Thursday, Romney fueled the buzz around Ryan, telling NBC that he wants a vice president with “a vision for the country, that adds something to the political discourse about the direction of the country.”

Several Republicans took that as an indication that Ryan had shot to the top of a shortlist said to include Ohio Sen. Rob Portman and former Minnesota Gov. Tim Pawlenty. Neither of those Republicans had plans to be in Virginia on Saturday.

Romney’s completion of the GOP ticket comes as he tries to repair an image damaged by negative Democratic advertising and shift the trajectory of a campaign that’s seen him lose ground to President Barack Obama. The vice presidential selection will dominate headlines, and Romney’s team has been relentlessly teasing the announcement for weeks.

Ryan, 42, is viewed by some in the Republican Party as a bridge between the buttoned-up GOP establishment and a riled-up tea party movement that has never warmed to Romney.

As the chairman of the House Budget Committee, Ryan could help Romney make the argument that only the GOP ticket knows how to turn around a nation in the midst of a sluggish economic recovery. As talk about Ryan swirled this week, Democrats have been castigating Romney for embracing the Ryan-sponsored budget proposal that critics say is painful to the poor and elderly. It was a sign of the line of attack to come.

The move also now links Romney directly with House Republicans, including no-compromise tea partyers who have pressed for deep spending cuts. Obama has been casting House Republicans as an impediment to progress in the often-gridlocked Washington.

At the same time, Ryan on the ticket could help Romney become more competitive in Wisconsin, a state Obama won handily four years ago but that could be much tighter this November.

Adding fuel to the speculation, Romney’s son Tagg also joined Ryan at a funeral for victims of the Wisconsin Sikh temple shooting with Ryan on Friday, though the younger Romney said he is planning to campaign in New Hampshire over the weekend and is not attending the bus tour. And a plane was tracked Friday on a flight from Boston to Janesville, Wis., where Ryan lives.

The Wall Street Journal, in an editorial on Thursday, praised Ryan as a strong choice for Romney: “The case for Mr. Ryan is that he best exemplifies the nature and stakes of this election. More than any other politician, the House budget chairman has defined those stakes well as a generational choice about the role of government and whether America will once again become a growth economy or sink into interest-group dominated decline.”

Party officials say Republican National Committee Chairman Reince Priebus has been convinced for days that Romney had settled on Ryan, according to multiple people who spoke with the chairman. Priebus, who, like Ryan, is from Wisconsin, was expected to attend Saturday morning’s announcement.

Outside Ryan’s home in Janesville, there were no cars in the vicinity with government plates. An Associated Press reporter knocked on the door to his home three times and go no answer just before midnight local time. There was a light on in a first-floor room of the two-story brick home atop a hill.

Earlier this week, a Ryan adviser said the family, including the congressman, was preparing for a weeklong vacation to Colorado that was to begin Saturday.

Pawlenty was maintaining his Saturday schedule campaigning for Romney in New Hampshire, an official close to Pawlenty’s political team said. The person spoke on the condition of anonymity because the person was not authorized to speak ahead of the formal announcement.

Most of Romney’s staff learned of the looming announcement during a 10 p.m. EDT conference call Friday about an hour before the campaign issued a statement. The identity of Romney’s pick was not disclosed during the call.

There were signs of a potential announcement as most of Romney’s senior staff joined him on the flight from Boston, and the campaign added a last-minute rally to their Virginia itinerary on Saturday.

Earlier in the day, Romney’s campaign briefed reporters on the bus tour, making no mention of the impending vice presidential announcement.

“The governor keeps very close counsel on that, and I have no guidance,” adviser Eric Fehrnstrom said of any potential event.

Romney’s bus tour was expected to include appearances with Portman, as well as two others who had been talked about as possible contenders for running mate: Virginia Gov. Bob McDonnell and Florida Sen. Marco Rubio.

The tour will take Romney through four must-win states in as many days: North Carolina, Virginia, Florida and Ohio. All are battlegrounds where Obama won in 2008. While Obama could afford to lose in one or more of them and still reach the 270 electoral votes needed for another term, Romney almost certainly needs all four to beat him.