U.S. Sen. Arlen Specter (search) has so far spent more than $15 million to defend the Senate seat that he nearly lost in the closest Republican primary challenge of his career, according to Federal Election Commission (search) records filed Thursday.

But Specter, Pennsylvania's four-term senator, still raised twice as much as his Democratic challenger, Rep. Joe Hoeffel (search), over the last three months, the records show.

Specter raised $2.3 million between April 8 and June 30, the most recent FEC campaign finance reporting period. He now has $3.3 million in his campaign bank account after spending $3.5 million in the reporting period that included the state's April 27 primary — which Specter, a political moderate, won by a mere 12,603 votes over conservative Rep. Pat Toomey.

In all, Specter has spent $15.3 million since the election cycle began in 1999, records show.

"It took Arlen Specter $15 million to barely eke by in the primary, and now, while Joe Hoeffel's fund-raising numbers have nearly doubled, Specter's didn't move," said Hoeffel campaign manager Celia Fischer. "The bottom line is Pennsylvanians are responding to Hoeffel's determination to change the course in Washington, and rejecting Specter's defense of a failed Bush-Cheney agenda."

Specter's camp countered that Hoeffel has yet to attract any more support than when the Democrat declared his candidacy a year ago.

Hoeffel collected more than $1 million during the three-month period, during which he hosted events with two of the Democratic Party's most lucrative fund-raisers — Sen. Hillary Rodham Clinton of New York and former presidential hopeful and Vermont Gov. Howard Dean.

The three-term congressman spent $541,303 during the quarter and has $1.3 million in the bank. But as many as 66 percent of state voters surveyed in a Quinnipiac poll this week said they did not know enough about Hoeffel to form an opinion of him.

"At this rate he will raise less money than our primary opponent, and general elections are always more expensive to run than primaries," Specter campaign manager Christopher Nicholas said in a statement.

The FEC reports also offer a snapshot of how Pennsylvania's most competitive elections for the U.S. House are shaping up, including:

— The 6th Congressional District in Philadelphia's suburbs, which ultimately may be the strongest challenge to a sitting House member in the state. Incumbent Rep. Jim Gerlach, a Republican, has $873,350 in the bank compared to challenger Democrat Lois Murphy, who has $560,568. But Murphy is coming on strong: she raised $477,555 over the last three months, compared to Gerlach's $353,882.

— The Lehigh Valley's open 15th District seat, where fund-raising is almost evenly matched between Republican state Sen. Charlie Dent and wealthy Democratic newcomer Joe Driscoll. Driscoll so far holds a slight money edge: he raised $451,233, bringing his total contributions to just over $1 million. He spent $337,731 and has $562,427 in the bank. But Dent held his own, raising $382,774 this quarter to bring his total to $942,404. He spent $274,729 and has $391,432 on hand.

— The media-expensive 13th District's open seat in northeast Philadelphia and part of Montgomery County, the most competitive House race in Pennsylvania this year and one of the most cutthroat in the nation. Both candidates — Democratic state Sen. Allyson Y. Schwartz and three-time Republican contender Melissa Brown — survived hard-fought primaries.

Schwartz raised an impressive $935,079 — two-thirds of which came in after the primary — and spent $667,953. She has $485,279 on hand. Brown raised $439,790 and has $368,538 in the bank, said campaign manager Carl Fogliani. He did not immediately know how much she spent.

—The 17th District, where Republican challenger Scott Paterno has only about $160,500 on hand after winning a six-way primary in April, said his campaign manager, Dean Ouellete. Paterno's report was not immediately available, but Ouellete said the son of Penn State football coach Joe Paterno raised about $371,000 over the three-month period.

Paterno's opponent, Democratic Rep. Tim Holden, raised $314,252 to defend his seat in the GOP-leaning district in central Pennsylvania, and spent $80,916. He has $754,098 on hand.