Obama told supporters at a Democratic National Committee fundraiser Monday that the party has great candidates but their voices are being drowned out by groups that are pouring money into competitive races.
Last year the Supreme Court reversed a centurylong trend of limiting the power of big money in politics by saying corporations and unions may spend heavily to influence presidential and congressional elections. Obama is asking Congress to pass legislation that would limit how much those groups could spend.
Monday's fundraiser is expected to raise $1 million for the DNC.
The evening event was to be Obama's first appearance with U.S. Rep. Joe Sestak as the Democratic nominee. Sestak is in a closely contested race with Republican Pat Toomey, a former U.S. House member.
Sestak won the Democratic nomination in May over five-term Sen. Arlen Specter, the Republican-turned-Democrat who was supported by Obama, Pennsylvania Gov. Ed Rendell and the Democratic Party.
Sestak is using that victory over the White House and the party to his advantage in a year where voters are being tough on incumbents. One of his recent TV ads shows a newspaper headline that says, "Nonstop Joe Sestak refuses to join 'the establishment."'
Already, millions of dollars in television ads are flowing into the race from outside the state, a sign that national party committees and interest groups have already made Pennsylvania a priority. Its Senate race may forecast which state will win the swing state in the 2012 presidential election.
Earlier Monday, Toomey, who opposes the major points of Obama's agenda, signed a pledge to support a repeal of the federal estate tax during a brief event on the work floor of a suburban Harrisburg mechanical and electrical contractor.
Afterward, Toomey said Obama's visit will only remind voters about Sestak's support for the president's agenda that he says is adding costs and unpredictability for business owners and, as a result, slowing the nation's economic recovery.
"He's been in lockstep with the agenda that is preventing us from having the kind of recovery we should be having, and could be having," Toomey said. "And my guess is that most voters are not very happy with that agenda or Joe Sestak's support for it."