After surviving a close scrape in the Republican primary, Sen. Arlen Specter (search) turned his attention to the fall contest and began a campaign Wednesday that could put him at odds with the White House that helped him pull through.

The four-term moderate narrowly defeated conservative Rep. Pat Toomey (search), 51 percent to 49 percent, in Tuesday's primary after Toomey branded Specter as too liberal. The race was perhaps the most serious challenge yet to any Senate incumbent this season.

Specter will face Democratic Rep. Joe Hoeffel (search) in November.

Less than a day after his primary victory, Specter touted his efforts to trim tax cuts, retain overtime pay for workers, resist school vouchers and continue embryonic stem-cell research - all in opposition to President Bush. The four-term Republican also called the situation in Iraq a "tinderbox" that could be a problem for the president in the fall elections.

"I intend to retain my independent voice, a voice I have always had," Specter said. "The 12 million people of Pennsylvania have not elected me to be a rubber stamp, and I will speak out where I think the necessity calls for it."

Despite his policy differences with the president, Specter said Bush's public support was key to his victory over Toomey. The race was so tight, he said, that the usually stoic Specter could not "stop my nervous system from gyrating a little" while watching vote tallies roll in.

Hoeffel, meanwhile, embarked on a 19-stop tour to raise his low statewide profile. The three-term suburban Philadelphia lawmaker predicted that Specter moved too far to the right in the Republican race to be successful in November.

"This primary has demonstrated that Arlen Specter is not the senator that he used to be," Hoeffel said. "He used to be a moderate maverick, but he is neither of those things. He's voting for a Republican program in Washington that's not working in Pennsylvania. He's their senator now - not ours."

The Democrats blasted Specter as a "political opportunist."

"He has taken every side of every issue for no other reason than to protect his political hide," said Brad Woodhouse, a spokesman for the Democratic Senatorial Campaign Committee. "He owes his political survival to George Bush, and he's now stuck with him and his right-wing policies."

Registered Democratic voters outnumber Republicans in Pennsylvania by nearly 389,000.

Specter has long enjoyed support within liberal-leaning unions and abortion-rights groups, and predicted he would attract Democrats and independents. He said he could help Bush in the fall by pulling moderates to the GOP ticket.

"My agreements with the president are more extensive than my disagreements," Specter said.

Specter spent $10 million to win the primary. As of April 7, he had $4.5 million in his campaign bank account to Hoeffel's $800,000.

That makes Specter tough to beat in November, said Wilkes University political scientist Thomas J. Baldino.

Specter's near-loss "will give Hoeffel some hope," Baldino said. "But as bad a beating as Specter took in term of his reputation, he will continue to raise and spend enough money to demonstrate he can win."