Toomey, a 48-year-old former congressman, investment banker and restaurateur from the Allentown area, defeated Democratic Rep. Joe Sestak after hammering him on his liberal voting record and his ties to House Speaker Nancy Pelosi and President Barack Obama.
Sestak, 58, now in his second term representing a suburban Philadelphia district, is a former Navy vice admiral who commanded an aircraft carrier group in war after the Sept. 11 attacks. It was Sestak who put an end to Specter's 30-year Senate career by defeating the Republican-turned-Democrat in a shocking upset in the primary this year.
Tuesday's balloting capped a bare-knuckled campaign in which voters were inundated with tens of millions of dollars in TV and Internet attack ads and campaign fliers as they decided on a successor to Specter, whose voting record exemplified Pennsylvania's middle-of-the-road electorate and kept him in the Senate for five terms.
The two candidates are ideological opposites who portrayed each other as too extreme for Pennsylvania.
Toomey sought to tap into voter dissatisfaction over unemployment and the shaky economy to argue that Sestak, and his support for Obama's policies, were to blame. The Republican contended that the Obama administration's "extreme leftward lurch" required someone like him to help bring balance to Washington.
Sestak worked to convince voters that he was stuck cleaning up an economic mess caused by Toomey and the Bush administration's policies. He sought to cast Toomey as an apologist for Wall Street whose zeal for tax-cutting and deregulation helped cause the recession and sent jobs overseas.
The race cost more than $50 million and included spending by the candidates, political parties, unions and national business advocates in the general election and the bruising Democratic primary.
Specter narrowly won his fifth term after overcoming a Toomey challenge in the GOP primary in 2004. The senator switched parties in 2009, shortly after Toomey declared he wanted a rematch this year, and acknowledged his chances of winning the nomination in the increasingly conservative GOP were slim.
Obama and other Democratic leaders shunned Sestak and endorsed Specter in the May primary. But Sestak billed himself as the true Democrat, and called Specter a Democrat out of convenience, not conviction. He won with 54 percent of the vote, after which the Democratic establishment enthusiastically embraced him.