GOP ticket: Republican presidential candidate Mitt Romney names Paul Ryan his No. 2

A fired-up crowd cheered Romney and Ryan, supporters on bleachers at one point stamping their feet to create a loud rumble.

One campaign official said Romney settled on Ryan on Aug. 1, more than a week ago, and informed Beth Myers, the longtime aide who had shepherded the secretive process that led to the selection. The official spoke on condition of anonymity, not authorized to be named in providing details.

Romney and Ryan had an unannounced meeting last Sunday, and the congressman accepted the offer, campaign officials said.

Asked during the day if accepting the offer was an easy decision, Ryan replied, "It was, it was, we've got to save the country."

In making his pick, Romney bypassed other potential running mates, including Ohio Sen. Rob Portman, Florida Sen. Marco Rubio, former Minnesota Gov. Tim Pawlenty, Virginia Gov. Bob McDonnell and New Jersey Gov. Chris Christie.

Officials said he had called all five to notify them of his decision.

"I am deeply excited and honored to join you as your running mate," Ryan said in his first words at Romney's side.

Democrats took a dim view of Ryan's record.

"The architect of the radical Republican House budget, Ryan, like Romney, proposed an additional $250,000 tax cut for millionaires and deep cuts in education, from Head Start to college aid," Jim Messina, the president's campaign manager, said in a written statement.

"His plan would also end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors."

There was one unscripted moment during the day, when Romney mistakenly introduced Ryan as the next president. He returned to the podium to say, "Every now and then I'm known to make a mistake. I didn't make a mistake with this guy. But I can tell you this, he is going to be the next vice president of the United States."

As chairman of the House Budget Committee, Ryan is primary author of conservative tax and spending blueprints that the tea party-infused Republican majority approved over vigorous Democratic opposition in 2011 and again in 2012.

They envision transforming Medicare into a program in which future seniors would receive government checks that they could use to purchase health insurance. Under the current program, the government directly pays doctors, hospitals and other health care providers.

Ryan and other supporters say the change is needed to prevent the program from financial calamity. Critics argue it would impose ever-increasing costs on seniors.

Other elements of the budget plan would cut projected spending for Medicaid, which provides health care for the poor, as well as food stamps, student loans and other social programs that Obama and Democrats have pledged to defend.

In all, it projects spending cuts of $5.3 trillion over a decade, and would cut future projected deficits substantially.

It also envisions a far-reaching overhaul of the tax code of the sort Romney has promised.

Romney and Ryan appeared comfortable with each other when they campaigned together earlier in the year. The former governor eagerly shared the microphone with the younger man and they shared hamburgers at a fast food restaurant.

In making an endorsement before his state's primary last spring, Ryan said, "I picked who I think is going to be the next president of the United States — I picked Mitt Romney. ... The moment is here. The country can be saved. It is not too late to get America back on the right track. ... It is not too late to save the American idea."