Updated In his second new TV spot of the day — this one now playing in Pennsylvania — Barack Obama takes a strong stand against Big Oil, saying he “won’t let them block change anymore.”

Senator Obama stands at a gas station and speaks directly into the camera for the duration of the 30-second spot. (Must be his new style — he takes a similar direct approach in his Indiana ad.)

Mr. Obama goes after Exxon Mobil in particular. in the ad, which starts off with old footage of cars lined up for gas at an Exxon station back in the 1970s.

People cried out for energy independence back then, Mr. Obama says, and “nothing’s changed — except now Exxon’s making $40 billion a year, and we’re paying $3.50 for gas.”

But he’s going to do something about it, he says. Mr. Obama proposes putting a tax on the windfall profits of oil companies, and he says he’ll end American dependence on foreign petroleum. He can take aggressive steps against Exxon Mobil, he points out, because he hasn’t accepted donations from oil companies or lobbyists.

“It’s time that Washington worked for you. Not them,” he says.

Hillary Rodham Clinton’s campaign was quick to send out an e-mail accusing Mr. Obama of making false statements in his ad, saying he has received more than $160,000 from the oil and gas companies.

Phil Singer, deputy communications director for Mrs. Clinton, put out this statement: “It’s unfortunate that Senator Obama is using false advertising to explain why he can be trusted to do something about energy prices. Senator Obama says he doesn’t take campaign contributions from oil companies, but the reality is that Exxon Mobil, Shell and others are among his donors. I wonder if they’ll fix the ad.”

Mr. Singer shouldn’t hold his breath. Bill Burton, press secretary for the Obama campaign, reaffirmed the ad’s message, saying “Senator Obama is the only candidate in the race who doesn’t accept campaign contributions from special interests PACs and Washington lobbyists, and that includes oil companies and oil lobbyists.”

“The energy bill that Senator Clinton has already been criticized for misrepresenting — one that Clinton supporters Representatives Murtha and Kanjorski also backed — actually raised taxes on oil companies and made the largest investment in renewable energy in our nation’s history,” said Mr. Burton in a statement. “Instead of continuing with the negative and misleading tactics that voters everywhere are rejecting, Senator Clinton should get behind the Obama plan to ease the burden of rising gas prices on working families.”

Here’s the script for “Nothing’s Changed”: