NORFOLK, Va. - Republican presidential candidate Mitt Romney on Saturday chose as his running mate Rep. Paul Ryan of Wisconsin, a "young gun" conservative whose presence on the ticket ensures voters will be choosing this fall between two starkly different visions of the role of the federal government and the right course to economic recovery.

The choice of Ryan was universally hailed as a bold one for the usually cautious Romney and one certain to excite the party's conservative base, which until now has been driven more by its distaste for President Obama than its enthusiasm for Romney.

"Ryan's boldness is exactly what America needs," said Rep. Michele Bachmann, R-Minn., who challenged Romney's conservative credentials during the Republican presidential primary.

Paul Ryan's 'Path to Prosperity'
How the House Republicans' budget blueprint slashes spending and remakes Medicare.
-Program unchanged for beneficiaries enrolled before 2022.
-Starting in 2022, it becomes a voucher program that helps beneficiaries buy private health insurance. If premiums exceed voucher payment, beneficiary pays difference.
-Payments would vary by income, covering 30% of premiums for richest to 92% for poorest.
-Government pays insurance companies directly.
-Steadily raise the eligibility age between 2022 and 2033 until it reaches 67.
-Starting in 2013, federal funding goes to states as block grant.
Social Security
-No change.
Federal Spending
-Reduced from 12% of GDP to 6 %, but plan does not identify specific programs to be cut.
-Repeals President Obama's health care reforms.
-Spends $5 trillion less over 10 years than Obama's proposed budget.
-Simplify tax code by having just two rates, 10% and 25%, instead of six ranging up to 35%.
-Eliminates unspecified tax deductions.
-Closes unspecified tax loopholes.
Source: Path to Prosperity, Congressional Budget Office

Romney introduced Ryan in Norfolk, Va., in front of the USS Wisconsin, the World War II-era battleship named for Ryan's home state. He called his new running mate "an intellectual leader of the Republican Party" who "understands the fiscal challenges facing America, our exploding deficit and crushing debt, and the catastrophe that awaits us if we don't change course."

(See video of Romney and Paul speaking in Norfolk)

Virginia Republicans enthusiastically greeted the news that their ticket would include the man who crafted the GOP's blueprint for slashing federal spending and reforming entitlement programs like Medicare. As the two rolled through the state, their foot-stomping crowds grew larger. In Manassas, their last stop of the day, about 4,000 people turned out to see them and thousands of others lined the streets.

"He's the one that's going to get us out of this economic chaos," Jean Gannon, 54, a real estate appraiser from Powhatan, said of Ryan. "He has the economic background to get this country back on its feet."

The Republicans head to Wisconsin and North Carolina Sunday. Romney then goes to Florida and Ohio while Ryan heads to Iowa.

If the choice of Ryan energized Romney's conservative base, it also enlivened his Democratic opponents, who quickly jumped on Ryan as an advocate of tax cuts for the wealthy who would slash the Medicare program on which so many elderly rely.

Democratic strategist Doug Schoen said Romney's choice of Ryan may embolden the right, "but it will also energize the left," particularly in states like Florida where many voters are retired and counting on Medicare.

Romney previously endorsed Ryan's budget plan, but with Ryan now on the ticket, that plan will get much greater attention. Neither Ryan nor Romney on Saturday talked about Ryan's budget plan, and Ryan, notably, will not be joining Romney during a campaign stop in Florida later this week.

"This may well hurt Romney in states like Florida, which he needs to win," Schoen said of Ryan.

Ryan's budget plan promises to lower Medicare costs by converting it to a voucher-like program that would help beneficiaries buy private health insurance. To counter a barrage of criticism from Democrats and concerns from the elderly, Ryan changed the plan so that the changes wouldn't affect anyone enrolled in the program before 2022.

"The downsides are obvious," University of Virginia political science professor Larry Sabato said. "Ryan's views on entitlements could widen the gender gap -- women are very supportive of the safety net -- and seniors are also skeptical. Those over 60 have been very supportive of Romney, to this point."