Mitt Romney announced Wisconsin Rep. Paul Ryan as his running mate Saturday, selecting the Republican Party's go-to man on budget issues in a decision that signals the campaign will make the nation's spiraling debt a centerpiece of its attacks on President Obama.

Romney made the selection official during a campaign stop Saturday morning in Norfolk, Va., before launching a four-day bus tour.

The Republican presidential candidate called his new running mate a man of "steadiness" and "integrity." Speaking Saturday morning, Romney praised Ryan as an "intellectual leader" of the party, one who understands the toll the debt is taking on the country but is optimistic about the future.

"He doesn't demonize his opponents. He understands that honorable people can have honest differences and he appeals to the better angels of our nature," Romney said. "He's never been content to just curse the darkness. He'd rather light candles."

To the backdrop of retired battleship USS Wisconsin, an energized Ryan then riled up the crowd with a feisty speech that promoted Romney as the solution to the problems under President Obama. Ryan, met with chants of "USA, USA," gave a sweeping vision speech on free enterprise, one laced with attacks on the White House incumbent.

More On This...

"No one disputes that President Obama inherited a difficult situation. And, in his first two years, with his party in complete control of Washington, he passed nearly every item on his agenda. But that didn't make things better," Ryan said. "In fact, we find ourselves in a nation facing debt, doubt and despair. ...

"Whatever the explanations, whatever the excuses, this is a record of failure."

Ryan accused the Obama team of being "more worried about their next election than they are about the next generation," and pledged a Romney-Ryan ticket would "lead" through the tough issues and correct course.

"It doesn't have to be this way," he said. "We can turn this thing around."

Romney initially fumbled his introduction of Ryan. In the closing line of his remarks, he referred to Ryan as the "next president." Romney quickly returned to the podium to correct himself.

The Romney campaign formally announced the selection via its mobile-phone app. An alert that crossed shortly after 7 a.m. ET said: "Mitt's Choice for VP is Paul Ryan."

Word had already gotten out that the Republican presidential candidate had chosen the seven-term congressman and budget policy guru as his running mate well before the announcement. Sources also say Romney notified the aide running his VP search of his decision on Aug. 1.

The selection comes roughly two weeks before the start of the Republican National Convention in Tampa, and gives Romney plenty of space to rally the party behind his pick before the official nomination.

The announcement comes as some polls, including a recent Fox News survey, show the Republican presidential candidate losing some ground to President Obama.

Ryan, 42, already considered a rising star in the Republican Party, is chairman of the House Budget Committee. He's been in Congress since 1999 and is best known this session for his controversial budget plan that includes an overhaul of Medicare.

Democrats have persistently tried to vilify that plan as a scheme to "end Medicare as we know it."

The Obama campaign repeated that line in its first official response to the Ryan selection Saturday morning.

"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. His plan also would end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors," the campaign said. "As a member of Congress, Ryan rubber-stamped the reckless Bush economic policies that exploded our deficit and crashed our economy. Now the Romney-Ryan ticket would take us back by repeating the same, catastrophic mistakes."

But Ryan, a bookish but telegenic lawmaker, has stuck by his proposal as the solution to an ever-growing deficit inflamed by out-of-control entitlement spending.

Ryan has made fiscal discipline the touchstone of his tenure on the budget committee. With Ryan at his side, Romney can focus on jobs-creation proposals while his running mate focuses on plans for balancing the government's books.

Romney was the youngest member of his freshmen class when he entered Congress in 1999 at age 28. He had served as a congressional aide before that.

Ryan still lives in his hometown of Janesville, Wis., with his wife and three children.

Fox News' Carl Cameron contributed to this report.