PORTLAND – The political season came to a close with last November’s election, but television viewers may get the impression that it never really ended.

In recent weeks, TV stations and cable outlets have been airing 30-second spots urging viewers to call the state’s U.S. senators and tell them how to vote on use of the Senate filibuster in judicial nominations, oil drilling in the Arctic National Wildlife Refuge and changes in Social Security.

“It’s part of the perpetual campaign,” said Sen. Olympia Snowe, who perceives that the number of such ads has increased exponentially in recent years. “Regrettably, it seems that the campaigning never ends and the governing never begins.”

Sen. Susan Collins, too, said “it’s disappointing to see these polarizing ads continually run.” But she, like Snowe, is quick to point out that special interest groups are within their rights to place their message before the public to try to influence her vote.

Maine is arguably the leading target for such ads because of where its senators stand on the political spectrum as well as the state’s relatively small population and concentrated media market.

As middle-of-the-road Republicans, Snowe and Collins often wield the swing votes that can make the difference in a Senate sharply divided along party and ideological lines.

“This is the price of their independence – the interest groups think they can be targeted on every issue,” said Christian Potholm, a political science professor at Bowdoin College. “You wouldn’t waste your money on the senator from Mississippi who’s going to vote with the president no matter what.”

On some highly divisive issues, such as the plan to bar use of the filibuster to block judicial nominations, the two senators have been targeted in ads bankrolled by opposite sides. Neither Snowe nor Collins have said publicly how they plan to vote on the issue, which could shape the makeup of the federal judiciary for decades.

The latest entry into the fray is Progress for America, a group with strong Republican ties that is in the midst of a two-week, $1.5 million TV campaign designed to make sure that Bush’s conservative nominees to the court receive swift confirmation. The campaign targets senators in six states, including Maine.

People for the American Way, a liberal group with ties to Democrats, responded swiftly with plans to launch counter commercials.

At least one broadcast executive says this year’s flurry of issue ads is not unusual and that Snowe and Collins have been similarly targeted in dozens of previous campaigns bankrolled by out-of-state groups.

Steve Thaxton, president and general manager of WCSH-TV, Portland, said the latest campaigns tend to stand out because there are no competing issues or candidate races. “It’s also relatively concentrated,” he said, “contrary to general elections or special referenda which are spread over long periods of time.”

Although they spend most of their time in Washington, Snowe and Collins say they see the ads when they return home on weekends or at times when the Senate is not in session.

“I am well aware that this feels like the middle of a political campaign,” said Collins, “rather than a year when neither Olympia nor I are running.”

Staff members in the senators’ offices in Maine and at the Capitol keep tabs on the number of phone calls they receive on each issue. Snowe and Collins acknowledged that a big media buy can unleash a flurry of calls, which sometimes can tie up phone lines.

Potholm said Maine’s TV market, concentrated in Portland and Bangor, is relatively inexpensive, allowing for statewide campaigns that could not be waged in larger states without pouring in far more money.

“Maine is a cheap state,” he said. “If you have a million dollars you can come in and buy a lot of television. For interest groups who have tens of millions, this looks like a good buy.”

Sandy Maisel, director of the Goldfarb Center for Public Affairs and Civic Engagement at Colby College, said both sides in the ad wars have deep pockets.

“They have money they don’t know what to do with,” Maisel said, and when one side puts on a series of spots, the other side often feels that it has no choice but to respond.

Neither senator believes that the ads are money well spent.

“I don’t have a lot of interest in what an outside group that is not based in Maine thinks about a particular issue,” Collins said.

Snowe laments that the ads shortchange the public because they demand a yes or no stance on a complex issue often before the Senate begins its debate.

“Somehow it removes from the legislative equation the idea of having thoughtful discussion and reconciliation of differences,” she said. “If you don’t take a position in nanoseconds, then you’re questioned as being suspect, and I think this is regrettable.”