They're running neck-and-neck in the polls and fighting a vicious TV ad war.

But Sen. Rick Santorum and challenger Bob Casey are also running very close in the race for cash.

The latest financial information indicates a very expensive race in Pennsylvania, and not just for the senate seat.

Records show Pennsylvania's junior senator has raised more than $15 million and has already spent about half of it - meaning he has a total of about $8.8 million.

Casey, a very well-funded challenger, still has about half of the $8.8 million he raised still available.

Analysts said this could be one of the most expensive political battles in the nation.

Stu Rothenberg, a political analyst, said there's plenty of money in Pennsylvania.

"Rick Santorum is a great campaigner with a lot of money. His problem is the environment and that he's controversial. Casey... will have enough money to run a top-tier campaign, unlike a number of Santorum's previous opponents," Rothenberg said.

Some local members of the U.S. House have strong fundraising advantages over their opponents, including Murtha's $1.8 million warchest.

That means all eyes remain on the battle royale for the U.S. Senate.

To read more about which local members of congress raised the most money, please click here for a complete report.