With the retired battleship USS Wisconsin as the backdrop, presumptive GOP presidential nominee Mitt Romney introduced Rep. Paul Ryan as his running mate. NBC's Peter Alexander reports.

Updated at 10:45 am ET Presumptive GOP presidential nominee Mitt Romney introduced his choice as running mate, House Budget Committee Chairman Paul Ryan, 42, Saturday morning at a campaign event in Norfolk, Va.

Romney portrayed the Wisconsin congressman as “an intellectual leader of the Republican Party” and a man who “understands the fiscal catastrophe that awaits us if we don’t change course.”

He called him a legislator who had shown the ability to work with members of both parties, saying, “In a city that’s far too often characterized by pettiness and personal attacks, Paul Ryan is a shining exception. He doesn't demonize his opponents.”

He added that “a lot of people in the other party ... might disagree with Paul Ryan; I don't know anyone that doesn't respect his character and judgment.”

NBC's Andrea Mitchell has the story of Rep. Paul Ryan's ascent to America's biggest political stage.

Romney told the crowd, “At a time when the president’s campaign is taking American politics to new lows, we're going to do something differently. We’re going to talk about aspirations and American ideals and about bringing people together to solve the urgent problems facing our nation.”

Ryan then dashed onto the platform from the battleship U.S.S. Wisconsin docked at Norfolk.

Ryan referred to Romney, the former head of Bain Capital, as “someone who knows from experience that if you have a small business you did build that” – a reference to President Obama’s recent statement on the campaign trail that “if you've got a business, you didn't build that. Somebody else made that happen.” Obama argued that businesses benefit from government infrastructure and public sector investments.

Alluding to the entitlements and debt problems that loom over the next few decades, Ryan said Obama and Democrats in Washington “have refused to make difficult decisions because they are more worried about their next election than they are about the next generation.”

Referring to the nation’s sluggish economy and its growing burden of debt, Ryan said, “We can turn this thing around, … but it will take leadership and the courage to tell you the truth.”

NBC News Mitt Romney and Paul Ryan appear at a campaign event in Norfolk, Va., on Saturday.

Ryan also trumpeted Republicans’ faith in private sector entrepreneurs, saying, “We look at one another's success with pride, not resentment, because we know, as more Americans work hard, take risks, succeed, more people will prosper, our communities will benefit, and individual lives will be uplifted and improved.”

That theme is similar to ones Ryan has sounded in the past. He has been outspoken in saying that America must be “an upward mobility society.”

He told CNBC’s Larry Kudlow last February, “We don't want a safety net that turns into a hammock that lulls people into dependency in this country. We want people to get up on their feet and grab that higher rung of the economic ladder.”

He said, “We don't believe in class division. We believe in growth and prosperity, helping people when they are down on their luck get back on their feet, and pro-growth economic policies that put America in the lead, that make us competitive, that stop tearing people down in this zero-sum thinking.”

A senior adviser told NBC News that Romney informed Beth Myers, who headed his search for a running mate, of his decision to select Ryan on Aug. 1.

Live vote: Is Ryan a good choice?

As the author of an ambitious plan to redesign the Medicare program for older and disabled Americans, Ryan has long been the target of Democratic attacks.

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Obama campaign manager Jim Messina issued a statement Saturday saying Ryan's Medicare proposal "would end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors."

If enacted, Ryan’s proposal would be the most far-reaching change in Medicare since the program was created in 1965.

In 2011, one Democratic group ran an ad showing a man – presumably Ryan – pushing a terrified elderly woman in a wheelchair off a cliff.

Ryan’s plan would gradually increase the Medicare eligibility age to 67. This phased-in increase in the eligibility age would start in 2023.

Ryan’s proposal would do away with Medicare’s open-ended payments for those born in 1958 and later, (that is, people who turn 65 in 2023 or later).

Presumptive GOP presidential nominee Mitt Romney introduced his choice as running mate, House Budget Committee Chairman Paul Ryan, 42, Saturday morning at a campaign event in Norfolk, Va.

Instead, beginning in 2023, people in Medicare would be given a choice of private plans competing alongside the traditional fee-for-service option.

Medicare would provide a payment to pay for or offset the premium of the plan chosen by the senior. The payments would be higher for low-income people and lower for high-income people. The payments would grow over time but would not necessarily keep pace with the increase in the cost of medical care.

The Congressional Budget Office, in an assessment last year, said Ryan’s plan would result in “much lower deficits and debt in the long run.” But the CBO also found that under Ryan’s redesigned Medicare, “most elderly people would pay more for their health care than they would pay under the current Medicare system.”

One prominent Democrat, Sen. Ron Wyden of Oregon joined with Ryan last year on a proposal to redesign Medicare.

Wyden said in an opinion piece in the Huffington Post that the Wyden-Ryan proposal was not a finished piece of legislation but “simply a policy paper intended to start a conversation about how Democrats and Republicans might work together to uphold the Medicare Guarantee.”

Live vote: Is Ryan a good choice?

The Oregon Democrat also added, “Wyden-Ryan doesn't eliminate the traditional Medicare plan, instead it guarantees that seniors who want to enroll in Medicare's traditional fee for service plan will always have that option.”

House Budget Committee Chairman Paul Ryan enters the presidential campaign as presumptive GOP nominee Mitt Romney's choice for Vice President.

He added that, “Wyden-Ryan doesn't privatize Medicare because Medicare beneficiaries already have the option of enrolling in private health insurance plans. Wyden-Ryan makes those private plans more robust and accountable by forcing them to -- for the first time -- compete directly with traditional Medicare.”

But Wyden also said, “Some Republicans will undoubtedly declare their support for Wyden-Ryan without knowing what that means or believing in its principles. Mitt Romney, for example, claims to have helped write Wyden-Ryan even though I have never spoken to him about Medicare reform.”

As part of its fiscal year 2013 budget resolution, which it approved in March, the House supported Ryan’s Medicare reform plan. The vote was 228 to 191, with no Democrats voting for the proposal and 10 Republicans voting against it.

Ryan has offered some of his ideas on tax reform in interviews with David Gregory on NBC's Meet the Press. Last May, Ryan said, "What we're saying about taxes is take the tax shelters and the loopholes away from the well-connected and the well-off so we can lower tax rates for everybody so we can allow small businesses to grow and compete."

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He also said on Meet the Press in 2011: "Instead of job-killing tax increases, why don't we just stop subsidizing wealthy people? I mean, let's go after the crony capitalism, the corporate welfare in the tax code, in spending. And why don't we income-adjust our spending programs so that we don't subsidize wealthy people as much? I think that's a better idea to get more savings in the budget, get our debt down without doing economic damage."

Ryan, first elected to the House in 1998, worked in college as a staffer for Sen. Bob Kasten of Wisconsin, and later as a speechwriter for Jack Kemp and William Bennett and as an aide to Sen. Sam Brownback of Kansas.

Ryan voted for the bailout of the financial sector in 2008, as well as the auto industry bailout. He also voted for the 2003 bill to add a prescription drug benefit to Medicare and has voted this year to repeal President Obama’s health care overhaul.

NBC's Garrett Haake contributed to this report.