WASHINGTON — Amid record gas prices and mounting criticism from the McCain campaign, Senator Obama is shifting his stance on key energy issues.

His campaign insists the moves demonstrate his pragmatism, but Republicans say the Illinois senator is merely following the polls.

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Mr. Obama yesterday called for releasing 70 million barrels of oil from the Strategic Petroleum Reserve, less than one month after he voiced opposition to tapping the emergency stockpile.

The presumptive Democratic nominee also said he is open to a Senate compromise that includes new offshore drilling, though he has spent weeks criticizing Republican drilling proposals.

Mr. Obama’s new tone and positioning come as Senator McCain has intensified his attacks on the Democrat’s energy policy in television ads and on the campaign trail. Republicans have tried to pin the moniker “Dr. No” on Mr. Obama as a response to his resistance to measures aimed at reducing fuel prices, included expanded drilling and a temporary lifting of the federal gas tax earlier in the summer.

Several recent polls have shown a dead heat in a race that Mr. Obama had been leading, suggesting that Mr. McCain’s more aggressive strategy may be gaining traction. A survey by the Pew Research Center last month also found that, as gas prices have risen steadily, so has public support for offshore drilling.

During a speech in Michigan, Mr. Obama unveiled an energy plan geared toward reducing prices in the short term while weaning America off foreign oil within a decade. In addition to tapping the Strategic Petroleum Reserve, he said he would give immediate $1,000 energy rebates to American families, an initiative that would be funded by a proposed windfall profits tax on oil companies.

The Obama campaign also released a new TV ad yesterday hitting back at Mr. McCain’s energy policy by linking his support for extending tax breaks to oil companies with contributions the industry has made to his campaign.

Mr. Obama said selling oil from the nation’s stockpile had in the past lowered gas prices within two weeks, but on July 7 he told reporters he was opposed to the idea on the grounds that such a move “has to be reserved for a genuine emergency.” He cited as an example a terrorist attack on oil supplies in Saudi Arabia. A campaign spokesman, Bill Burton, said what Mr. Obama proposed yesterday was not a straight emergency sale of oil but a limited swap in which light crude oil would be sold now and later replaced by a heavier, cheaper oil.

A McCain spokesman characterized the proposal as a political ploy. “The strategic oil reserve exists for America’s national security strategy — not Barack Obama’s election strategy,” the spokesman, Tucker Bounds, said. “The last release of oil from the strategic reserve came in response to Hurricane Katrina, but the only crisis that has developed since Barack Obama last rejected this idea 28 days ago is a slide in his poll numbers.”

In the speech, Mr. Obama also praised a Senate deal in the works that would combine a rollback of tax breaks for oil companies, expanded investment in alternative fuels, and some new offshore drilling. He repeated his opposition to drilling but said he would support the bill if its inclusion is needed to pass. “I am not interested in making the perfect the enemy of the good,” he said, “particularly since there is so much good in this compromise that would actually reduce our dependence on foreign oil.”

Republicans characterized this shift, too, as a response to polls, and they panned Mr. Obama’s call for higher taxes on oil profits, saying they would simply lead to higher prices at the pump. A windfall profits tax could have a local impact as well, as New York’s public pension funds are heavily invested in oil companies. The top domestic equity holding for the New York State Teachers’ Retirement System, for example, is ExxonMobil.