HOUSTON—Republican Sen. John McCain called for a clean break from Bush administration energy policies on Tuesday, then promptly pivoted to accuse campaign rival Barack Obama of supporting recycled measures that failed in the past.

“Tax relief just isn’t change he can believe in,” said the Republican presidential nominee-in-waiting, mocking his opponent’s campaign slogan.

McCain’s bid to chart a middle course on a major issue hit a bump, though, when he criticized Obama for proposing a windfall profits tax, despite saying last month he would consider the same proposal.

In a speech in energy-producing Texas, McCain said the United States needs more oil than during the Arab oil embargo of the 1970s, yet produces less. Now, he warned, a single successful terror attack at an oil installation could plunge the country into an “economic crisis of monumental proportions.”

With President Bush’s poll ratings at historically low levels, McCain often emphasizes his differences with the current administration, and he coupled his speech with the release of a new television commercial stressing an issue that appeals to environmentalists.

“John McCain stood up to the president and sounded the alarm on global warming—five years ago,” the ad states. “Today, he has a realistic plan that will curb greenhouse gas emissions. A plan that will help grow our economy and protect our environment.” Aides said the commercial would run in several battleground states and on cable television over the next several days.

McCain included little in the way of new proposals in his speech. He called for reform of the laws governing the oil futures trading market, and drew a standing ovation when he repeated his day-old support for an end to the federal moratorium on offshore oil drilling. He favors allowing states to decide whether to explore offshore waters.

That drew a rebuttal from Obama, who said his opponent had switched positions from when he first ran for president in 2000. “I think he continues to find himself being pushed further and further to the right in ways that in my mind don’t show a lot of leadership,” he said.

Obama also said there is “no way that allowing offshore drilling would lower gas prices right now. At best you are looking at five years or more down the road.”

McCain said he would outline additional specific measures in the next two weeks and, instead, used the speech to make the case for eliminating U.S. dependence on foreign oil, call for a break from Bush policies and criticize Obama.