Associated Press
Republican presidential candidate and former Massachusetts Gov. Mitt Romney campaigns at Farm Bureau Live at Virginia Beach, Va., Thursday, Nov. 1, 2012.

HARRISBURG, Pa. — Republican presidential nominee Mitt Romney and running mate Paul Ryan planned campaign visits to Pennsylvania this weekend just as the Republican National Committee said Thursday that it will spend an eye-popping $3 million on TV ads in the state for the final few days of the presidential campaign.

The news came with five days left in a presidential campaign that has seen the traditional battleground state go from a relative backwater to front and center in an 11th-hour blitz by Romney and his conservative allies. Pennsylvania, which is tied for fifth-most electoral votes in the nation, has supported Democrats in the past five elections, and winning its 20 electoral votes is crucial to President Barack Obama's re-election bid.

The last-minute ad buys by the RNC, the Romney campaign and five other pro-Romney groups could bring their combined spending to $12 million in the campaign's final days, swamping the ad spending being marshaled by the Obama campaign.

The Obama campaign called it "an act of sheer desperation." Obama has led the state's independent polls all year, but Romney campaign officials say they believe they have an opportunity to win.

Jill Biden, the wife of Vice President Joe Biden, also will visit Pennsylvania on Friday and Saturday.

Much of the activity will focus on the heavily populated Philadelphia suburbs, where Democrats are increasingly spreading out from Philadelphia and blending with moderate Republicans to create a crucial, four-county swing area that is home to 20 percent of Pennsylvania voters. All but one candidate for U.S. Senate, governor and president who has won Pennsylvania going back at least a decade also carried Bucks, Chester, Delaware and Montgomery counties. The exception was Republican U.S. Sen. Pat Toomey in 2010.

Romney was expected to appear at a Sunday rally at Shady Brook Farm in Yardley, 20 miles northeast of Philadelphia on the New Jersey border, campaign officials said. Ryan will appear Saturday at a private terminal at Harrisburg International Airport. Jill Biden was to appear in Media on Friday afternoon and West Chester, Norristown and Philadelphia on Saturday.