"After four years of getting the runaround, America needs a turnaround, and the man for the job is Governor Mitt Romney," the 42-year-old Wisconsin lawmaker declared in what amounted to a debut on the national stage. However, the nation's attention was divided: He spoke at a convention dogged by Tropical Storm Isaac, downgraded from a hurricane but still inflicting misery on millions along the nearby northern Gulf Coast.
"We will not duck the tough issues; we will lead," Ryan said.
His speech was part attack on Democratic President Barack Obama and part spirited testimonial to Romney, all leavened by a loving tribute to Ryan's own mother, Betty, 78, seated across the hall in a VIP box. "To this day, my mom is a role model," he said while she beamed and exchanged smiles with one of his children as delegates cheered their approval.
A generation younger than Romney, he emphasized their differences as well as their commitment to tackle the economy.
"There are songs on his iPod which I've heard on the campaign bus - and on many hotel elevators," he said to laughter in the hall.
As for his own favorites, he said Romney "actually urged me to play some of these songs at campaign rallies. I said, 'I hope it's not a deal breaker, Mitt. But my playlist starts with AC/DC and ends with Zeppelin."
Turning serious, he said of Obama and the Democrats: "They've run out of ideas. Their moment came and went. Fear and division is all they've got left."
To the cheers of the delegates, he pledged Republicans would save Medicare from looming bankruptcy, despite constant accusations from Democrats that the GOP approach would shred the program that provides health care to more than 30 million seniors.
"Our nation needs this debate. We want this debate. We will win this debate," Ryan declared. But he offered no details of the remedy Republicans would propose.
Romney, in a secondary role if only for a moment, accused Obama of backing "reckless defense cuts" amounting to $1 trillion. Addressing the American Legion in Indianapolis, he said, 'There are plenty of places to cut in a federal budget that now totals over $3 trillion. But defense is not one of them."
In Tampa, the Romney team scripted an economy-and-veterans-themed program and kept a wary eye on Isaac. The storm remained a threat to levees in the New Orleans area almost exactly seven years after the calamitous Hurricane Katrina.
Inside the convention hall, delegates cheered a parade of party leaders past, present and - possibly - future.
The presidents Bush, George H.W., elected in 1988, and his son, George W., winner in 2000 and 2004, were featured in an evocative video. Arizona Sen. John McCain, the party's 2008 nominee, spoke on his 76th birthday and said he wished he'd been there under different circumstances. And an array of ambitious younger elected officials preceded Ryan to the podium, Sens. Rand Paul of Kentucky and John Thune of South Dakota among them.
Former Secretary of State Condoleezza Rice praised the Republican ticket in a speech that made no overt mention of Obama. "Mitt Romney and Paul Ryan will rebuild us at home and inspire us to lead abroad. They will provide an answer to the question, 'Where does America stand?'"
The congressman's speech skipped lightly over inconvenient facts.
He assailed the stimulus legislation that Congress passed at Obama's request in 2009 to help stabilize the economy but neglected to mention that he asked for some of the resulting funding, which eventually went to two Wisconsin energy conservation companies in his home state.
He also accused Obama of taking more than $700 billion from Medicare to help finance the president's signature health care law. But he didn't mention that a pair of tax and spending plans he authored as chairman of the House Budget Committee retained the cuts and put the money toward deficit reduction.
Ryan said he was accepting "the calling of my generation to give our children the America that was given to us."
He added, "The present administration has made its choices. And Mitt Romney and I have made ours: Before the math and the momentum overwhelm us all, we are going to solve this nation's economic problems.
"And I'm going to level with you: We don't have much time."
As he spoke a pair of electronic boards tallied the nation's growing national debt, approaching $16 trillion overall and more than $5 billion since the convention opened.
Ryan's vice presidential acceptance speech marked a prime-time national debut by a relatively young lawmaker lauded by fellow Republicans for his understanding of the complexities of the nation's budget.
Romney tapped Ryan this month as his running mate, a selection that cheered conservatives who have doubted the presidential candidate's own commitment to their cause.
If Ryan's selection was designed in part to appeal to conservatives, the convention was scripted to strengthen the ticket's appeals among women, Hispanics and others who prefer Obama over the Republicans, as well as veterans who supported McCain in 2008.
Romney delivers his own nationally televised acceptance speech Thursday night in the final act of his own convention. The political attention then shifts to the Democrats, who open their own convention on Tuesday to nominate Obama and Vice President Joe Biden for a second term.
Deep into a two-week stretch of national gatherings, the race for the White House is in a sort of political black hole where the day-to-day polls matter little if at all as voters sort through their impressions.
Despite the hundreds of millions of dollars spent on television commercials by the candidates, their parties and supporting groups, the race has appeared unusually close since Romney clinched his nomination last spring.
Only eight or so battleground states appear to be competitive, although Republicans say they hope to expand the campaign after Labor Day, particularly in industrial states struggling to recover from the worst economic recession since the Great Depression.
As chairman of the House Budget Committee, Ryan is the architect of a plan to curb long-term deficits by reducing taxes and making deep cuts in accounts ranging from farm programs to education. He also advocates saving billions from remaking Medicare and Medicaid, the government's health care programs for seniors and the poor.
The Medicare changes, in particular, are potentially incendiary in an election campaign. Democrats say that Romney, with his selection of Ryan, has accepted political ownership of a plan that would turn the program from one in which seniors' medical bills are automatically paid into one in which the government would give them checks to purchase coverage at costs that would require them to dip deeper into their pockets.
For all of the attack ads and inflammatory rhetoric, the two campaigns tiptoed carefully around the storm ravaging the Gulf Coast, vying to demonstrate concern for the victims without looking like they were seeking political gain.
Obama told an audience in Virginia he had spoken on the phone with governors and mayors of the affected states and cities while aboard Air Force One earlier in the day. Romney's aides let it be known he might visit the region once the storm had passed.
Romney's reference to $1 trillion in defense cuts was a 10-year figure that combined reductions already enacted by Congress and reductions scheduled to begin next January as a result of Congress' failure to reach agreement on a broad plan to cut deficits.
He did not say so in his speech, but most Republicans, including Ryan, voted for the first installment as well as the second.
And another convention speaker, Sen. Paul of Kentucky, pointedly disagreed with Romney on defense spending.
"Republicans must acknowledge that not every dollar spent on the military is necessary or well-spent, and Democrats must admit that domestic welfare and entitlements must be reformed," he said.
Romney's reference to 9/11 was glancing in a speech that accused Obama of unwise defense cuts. Romney noted the economy is the top issue in the race, but he said, "Our debates can change suddenly, with a ringing phone in the dead of night ... or a plume of smoke on a clear blue morning.
"The first job of government is to keep the American people safe," he said, pledging to do so.
Democrats spent part of their time working to tarnish the Republican brand. They pointed to an ABC News report that said Romney's campaign had held a reception in Tampa Tuesday night aboard a yacht flying the flag of the Cayman Islands.
Romney has been criticized for having investments there by Democrats who say the effect is to reduce his taxes.
In an appearance before University of Virginia students, Obama said he understood Republicans didn't have much nice to say about his tenure in office. He told his listeners the GOP hoped to disparage him so much that they would either vote for Romney or sit out the election.
Romney had already returned to Florida aboard his chartered jet when Senate Republican Mitch McConnell of Kentucky began the convention's daily battering of Obama.
"America is suffering through an economic calamity of truly historic dimensions," he said in excerpts released in advance of his convention appearance.
"Some are calling it the slowest recovery in our nation's entire 236-year history. To call this a recovery is an insult to recoveries." He spoke a few hours after the government reported economic growth for the second quarter was 1.7 percent, sluggish but marginally better than earlier estimated.
Associated Press writers Steve Peoples in Indianapolis, Julie Pace in Charlottesville, Va., Jim Kuhnhenn in Washington and Philip Elliott, Beth Fouhy and Tamara Lush in Tampa contributed to this story