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But Big Oil seems a particularly inviting target for Democrats seeking to defend their Senate majority in next year’s elections.

Thursday’s marquee hearing featured the CEOs of Shell Oil Co., ExxonMobil, ConocoPhillips, BP America and Chevron Corp., five companies that booked profits totaling $36 billion during the first quarter. The Democrats say that with profits that high, the big oil companies wouldn’t miss tax breaks that average $2 billion a year.

“My guess is you will be able to protect yourselves. … You’re used to prevailing,” said Sen. John D. Rockefeller IV, West Virginia Democrat. Oil companies, he added, are “deeply and profoundly committed to sharing nothing.”

Gasoline prices are above $4 a gallon in much of the country. The national average is about $3.96 a gallon for regular unleaded, up from $2.90 a gallon a year ago, according to AAA.

The nonpartisan Congressional Research Service concluded that eliminating the tax breaks would be unlikely to result in higher gasoline prices, which are influenced by a host of factors. The report, released Wednesday, said that eliminating the tax breaks would raise about $1.2 billion in 2012. By comparison, the five oil companies had combined revenues of $1.5 trillion and profits of more than $76 billion in 2010, the report said.

Mr. Menendez’s bill would prohibit the five oil companies from taking a tax deduction originally aimed at boosting domestic manufacturing. The bill also would eliminate a tax break that allows oil companies to reduce their American taxes by deducting royalties paid to foreign governments.

Republicans, who now control the House and have enough votes to block legislation in the Senate, oppose tax increases. They are joined on this issue by a handful of Democrats, mainly from oil-producing states. Seven Senate Democrats joined with Republicans to defeat a tax proposal similar to Mr. Obama’s in February.

On Wednesday, Sen. Mary L. Landrieu, Louisiana Democrat, called on fellow party members to “stop introducing gimmicks like this that might get you a few political points in the short run, but it is not leading us in the right direction.”

Associated Press writer Laurie Kellman contributed to this report.