With 31 days until the Pennsylvania Democratic primary, Sen. Barack Obama yesterday began airing the first pre-primary ads on Philadelphia TV stations.

According to public records, the campaign spent about $330,000 on 30- and 60-second spots that will run on six area stations through Monday, the state deadline for voter registration.

Sen. Hillary Rodham Clinton, with a double-digit lead in state polls, has yet to hit local airwaves in the run-up to the April 22 primary. A total of 158 Democratic delegates are in play.

After Clinton won the most votes in the Ohio and Texas primaries March 4, it was estimated that the candidates together would spend $7 million on TV ads in Philadelphia over the next seven weeks.

Given the shorter time frame, the new total will be closer to $3 million to $4 million, veteran local Democratic consultant Neil Oxman predicted.

"We're surprised they didn't start marketing in the state immediately following Ohio and Texas, when Pennsylvania was the next key battleground," said Joe Collins, NBC10's vice president for sales.

Since Pennsylvania is no longer the make-or-break primary, the race might not be decided until after June 9. Campaigns are revising their spending strategy.

Thus far, Obama is outspending Clinton on TV by almost 2-1, Oxman says. "The one thing that dictates what you do in a campaign is how much money you raise. He's raised a lot more money."

Oxman labels Obama's four-day commercial outlay as "an A-minus, B-plus" buy. "In Philly, a punch in the face is about $500,000 a week."

The largest piece of Obama's $330,000 broadcast-TV total - 40 percent - went to longtime ratings leader 6ABC. CBS3 followed with 22 percent; NBC10, 21 percent; FOX29, 12 percent; myphl17, 3 percent; and the CW, 2 percent.

Given that Obama is strong among young men, he bought two 30-second spots on CBS3's airing of the NCAA basketball tournament: one for $18,000 during last night's Villanova-Clemson game and another for $9,000 during today's coverage.

Over the four days, the campaign paid $86,595 for a total of 33 ads on CBS3, according to records. At sister station the CW, it was $5,370 for 13 spots. At NBC10, $83,025 for 47 ads; at FOX29, $39,430 for 39 ads.

Records at 6ABC and myphl17 were not made available.

As for when Clinton will start airing spots here, Mark Nevins, her Pennsylvania press secretary, said: "I live by the old adage that the colonel never gives away the secret recipe. We will have ads in Philly soon."

Obama's spots quickly drew fire from the Clinton campaign.

In a conference call with reporters yesterday, Nevins called an ad about Obama's efforts at ethics reform "misleading at best."

Phil Singer, Clinton's deputy national communications director, said he wanted to "put the alert out" concerning the type of commercials he expects Obama to use in Pennsylvania in the weeks ahead.

"During the course of the campaign, he has made a number of misleading charges against our campaign," Singer said. "It's important that we continue to be vigilant in pushing back."

Sean Smith, state spokesman for Obama, said the Clinton campaign had "taken more money from PACs and Washington lobbyists than any other campaign" in the 2008 cycle.

Senior staff writer Larry Eichel contributed to this report.