The race to replace U.S. Sen. Arlen Specter has drawn millions of dollars to Pennsylvania to pay for televised campaign ads.
Federal campaign-finance reports are due today for the third quarter of the year. Toomey has already announced that he raised $3.8 million during that period while Sestak has announced that he raised $3.2 million.
They're already spending that money on campaign ads, joined by national Republican and Democratic groups running attack ads.
But it is the outside money, enabled by a U.S. Supreme Court ruling in January that allowed corporations to spend cash on campaigns, that has drawn much of the interest, along with the ire of many Democrats and the embrace of many Republicans, during this election season.
Legislation to restore the disclosure of whose money pays for campaign ads is stalled in the U.S. Senate. Sestak says he would vote for the so-called "Disclose Act" while Toomey says he does not support it as written.
Sestak on Tuesday said Toomey should call for the U.S. Chamber of Commerce to disclose who funds its ads that criticize Sestak's support of "card check" legislation to make it easier for unions to organize in workplaces.
Sestak's campaign later said he believes "all organizations spending money on political campaigns should have to disclose who is funding them - no matter if the ads are for him or against him."
Toomey this week said ads from outside groups resulted from "overregulation" and federal campaign finance limits on how much a donor can contribute to a candidate.
He supports removing those limits, while requiring regular disclosure about where the money comes from.
"Since we don't permit that and we've put these restrictions on campaigns, you have a number of unintended consequences," Toomey said. "One is that candidates can lose control of the message because my spending in the race could be dwarfed by spending by other groups."
Some of those groups include:
_ The U.S. Chamber of Commerce, which is spending $75 million this election season to influence races and started running ads critical of Sestak in July. The ads are on the air now in central and western Pennsylvania.
The chamber's latest ad comes after the liberal ThinkProgress blog suggested that dues collected from overseas chapters in such countries as China and Bahrain flow into the same bank account used to pay for the political ads.
Sestak told voters this week that "foreign corporation money may be funneling through the Chamber of Commerce," echoing claims made by President Obama at a Philadelphia rally on Sunday.
Bruce Josten, a top chamber official, accused Democrats of "an attempt to demonize specific groups and district Americans from a failed economic agenda."
The chamber, which denies using foreign money to pay for the ads, would not say how much it is spending in Pennsylvania to attack Sestak.
_ American Crossroads and its off-shoot, Crossroads GPS, are spending $52 million this election season, according to Karl Rove, a former senior adviser to President George W. Bush who is pushing the effort along with Ed Gillespie, a former chairman of the Republican National Committee.
American Crossroads discloses its donors - including five donations since August of $1 million or more - to the U.S. Federal Elections Commission, while Crossroads GPS does not.
Crossroads GPS ran ads in August critical of Sestak for his vote in support of Obama's health-care reform act.
Rove, speaking at the National Constitution Center on Sept. 27, said the country has an "unhealthy" approach to campaign finance that sets one set of rules for rich people, one set of rules for organized labor and one set of rules for everyone else.
"What we have now is a system in which we've driven the money out of the public view and into the private sphere," said Rove, who complained about media attention his efforts have drawn.
_ The Club for Growth, a conservative group run by Toomey after he left Congress, ran ads in August attacking Sestak's "liberal schemes," supporting the federal stimulus bill and bail-outs in the home-mortgage industry.
_ The Emergency Committee for Israel slammed Sestak in July TV ads for a 2007 speech he made to the Philadelphia chapter of the Council on American Islamic Relations. A spokesman for the group, run out of the same public-relations firm in Washington, D.C., that lobbied for war in Iraq, declined to identify its donors.
_ VoteVets.org, founded by veterans of the wars in Iraq and Afghanistan, spent about $400,000 to air ads slamming Toomey this week for voting against a $1,500 combat-pay bonus. That followed $500,000 in campaign literature the group circulated two weeks ago, also attacking Toomey.
"The rules are the rules," VoteVets spokesman Eric Schmeltzer said this week while refusing to disclose his group's donors. "You can't play with one arm tied behind your back."