In the end, MSNBC host Chris Matthews said yesterday, he could not surrender the job he loves for a long slog through the trenches of Pennsylvania politics in an effort to unseat five-term Republican Sen. Arlen Specter.

"There's a wonderful power in being able to get up in the morning and do and say what you believe," Matthews said in an interview. "As long as I'm decent and don't use bad words, I can do pretty much anything I want."

So on Wednesday, Matthews ended months of flirtation, telephoning Pennsylvania Democrats who had discussed a possible campaign with him to say he would not be running next year. He also told his

Hardball

show staff.

Hardball

and other MSNBC broadcasts were already under attack by Republicans who argued that the network was a propaganda machine for Barack Obama during the race for the presidency. Media ethicists said it would be inappropriate for Matthews to remain on the show if he really were a candidate.

Matthews said he wanted to protect his "integrity" above all, and news coverage Monday of Specter criticizing Obama's nominee for attorney general intensified his concern.

"That was the point I realized I had to make a decision now, one way or the other," he said.

Although some party leaders thought Matthews' celebrity would be an asset, there are several Democrats who are said to be mulling a Senate race and now will have to make decisions of their own.

Among them: Philadelphia District Attorney Lynne M. Abraham, U.S. Rep. Patrick Murphy of Bucks County, State Rep. Josh Shapiro of Montgomery County, Constitution Center CEO Joseph M. Torsella, and Auditor General Jack Wagner of Allegheny County.

Matthews, 63, grew up in Northeast Philadelphia, joined the Peace Corps after graduating from Holy Cross College, and had a political career before becoming a Washington journalist.

He was a Democratic Capitol Hill aide, a speechwriter for President Jimmy Carter, and a top adviser to the then-House Speaker Tip O'Neill (D., Mass.).

Before creating

Hardball

11 years ago, Matthews was a columnist and bureau chief for two San Francisco newspapers.

The Senate talk came as Matthews was negotiating with the network over a new contract. Matthews said a deal should be completed next week. "I'm going to be here a long time," he said.

Some analysts say they believe that Specter, 78, is more vulnerable than ever despite his moderate record on many issues, because centrist Republican voters in the Northeastern United States have been deserting the party in recent years. In the four suburban counties around Philadelphia, the GOP has lost 61,000 registered voters since 2004; Democrats now have a statewide advantage of 1.2 million registered voters.

The GOP primary electorate has grown more conservative, analysts say. And in 2004, Specter barely survived a primary challenge from Pat Toomey, then a conservative Lehigh Valley congressman and now head of the antitax Club for Growth. Toomey has left the door open to another go.

"I'm going to have a tough opponent in the general election and a tough opponent in the primary before that," Specter, who has $6 million in the bank, said yesterday. "This is a tough state - it's a real battle to stay on top of the wave. I'll be ready."

Any Democrat who makes the race is "basically playing the lottery" that Specter will lose to a more beatable right-wing Republican, said Philadelphia political consultant Larry Ceisler. But that might not happen, he said, especially with the Democrats just one seat away from having a filibuster-proof majority in the Senate.

"Conservatives have looked at this, and I don't see any great desire on their part to lose that seat and become irrelevant in the Senate," said Ceisler, a Democrat.

Besides, Ceisler said, "running against Arlen Specter is like having your teeth pulled without novocaine. He is a warrior."

Contact staff writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com.