In other primary races Tuesday, Oregon's Democratic Gov. Ted Kulongoski defeated two rivals to seek a second term. An Iraq war veteran won the Democratic nomination for Congress in Pennsylvania, while another was defeated in a congressional primary in Kentucky.
Meanwhile, at least 14 state lawmakers in Pennsylvania lost their jobs — including both of the Senate's top Republicans — amid voter anger over a big pay raise. The pay hikes were passed in the middle of the night last year, then repealed by legislators under public pressure.
Casey, the state's treasurer and son of the late Gov. Robert P. Casey, was courted by national Democratic Party leaders to take on Santorum, the Senate's No. 3 Republican and a close ally of President Bush. The race could cost a combined $50 million.
With 91 percent of precincts reporting, Casey had 587,622 votes, or 85 percent to cruise past Philadelphia pension lawyer Alan Sandals and Philadelphia college professor Chuck Pennacchio.
"Tonight voters from across the state overwhelmingly showed President Bush, Rick Santorum and the whole 'wrong direction' gang in Washington that the values that unite us as Democrats are stronger than anything that might divide us," Casey said in a statement.
Santorum, seeking a third term, renewed his challenge for Casey to engage in debates.
"Come out from behind the name and stand before the voters of Pennsylvania and talk about the issues important to the people of this state," said Santorum, who was unopposed in his primary.
Sixty-one incumbents in the 253-member Pennsylvania legislature faced primary challenges, the most since 1980. The 14 defeated members, plus an unusually large number of retirements, mean more than one out of six seats will turn over this fall. Six races involving incumbents were too close to call early Wednesday.
Swept from office were the Senate's No. 1 Republican — President Pro Tempore Robert C. Jubelirer — and Majority Leader David J. Brightbill. It's the first time in more than 40 years that any Pennsylvania legislative leader was voted out of office.
In Oregon, Kulongoski drew 54 percent of the vote to beat a former state treasurer and a county commissioner. He now faces Portland lawyer Ron Saxton — who easily won the GOP nod — and independent Ben Westlund.
A Pennsylvania congressman mired in a sex scandal won his primary challenge. Republican Rep. Don Sherwood acknowledged a five-year extramarital affair after his mistress accused him of choking her at his Capitol Hill apartment.
Iraq War veteran Patrick Murphy, a Democrat, also won his primary to face freshman Republican Rep. Mike Fitzpatrick in a swing district in the Philadelphia suburbs.
In Kentucky, Iraq War veteran Andrew Horne failed in his bid to take on Republican Rep. Anne Northup in a Louisville-area district. Democrat John Yarmuth, a political columnist, won.