NORFOLK, Va. (CBS NEWS) - Presumptive Republican nominee introduced his new running mate, Wisconsin Rep. Paul Ryan, on Saturday as a man of character and integrity. Romney pledged that he and Ryan would go to every corner of the country to improve the economy and strengthen the middle class.

As Romney introduced Ryan as a man who learned character and values early - the Wisconsin congressman's father died when he was 16 years old - he also sought to emphasize Ryan's middle-class roots.

"He internalized the virtues and hard-working ethic of the Midwest. Paul Ryan works in Washington, but his beliefs remain firmly rooted in Janesville, Wis.," Romney said, citing Ryan's hometown.

He praised his work in Congress as a combination of "firm principles with a practical concern for getting things done." And even though Ryan is viewed as one of the ideological leaders of his party, Romney praised him as "a shining exception."

"He doesn't demonize his opponents. He understands that honorable people can have honest differences," Romney said.

The Obama campaign issued a statement depicting Ryan in a drastically different way. "In naming Congressman Paul Ryan, Mitt Romney has chosen a leader of the House Republicans who shares his commitment to the flawed theory that new budget-busting tax cuts for the wealthy, while placing greater burdens on the middle class and seniors, will somehow deliver a stronger economy," campaign manager Jim Messina 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," Messina added.

In an attempt to preempt some of the attacks from Democrats over Ryan's controversial budget that makes deep cuts to entitlement programs, Romney pledged to the crowd, "We will preserve Medicare and Social Security and keep them there for future generations."

Romney's otherwise spotlessly executed announcement had one flub: he introduced Ryan as the next president of the United States. When Ryan took the stage, Romney corrected himself.