The two men are in a bitter, longer-than-expected fight for the nomination to challenge President Barack Obama in November.

The latest Gallup tracking poll showed Romney — boosted by an outright win this week in Arizona and a slim win in his home state of Michigan — with 35 percent support, to 24 percent for Santorum. The Gallup survey represents a daily snapshot of a candidate’s standing.

But polls show Santorum with a considerable advantage in Ohio, probably the most important state that votes Tuesday. The votes in 10 states will apportion a total of 419 delegates to the party national convention in August. The Republican nominee must accumulate at least 1,144 delegates to win the nomination.

Romney now leads with 168 delegates, followed by Santorum with 86. Former House of Representatives speaker Newt Gingrich has 32 delegates, and libertarian Rep. Ron Paul has 19.

Obama, meanwhile, has been focusing on energy policy as U.S. gasoline prices have hit a record high for this time of year. Some forecasters predict prices could climb to $5 a gallon (3.79 liters). That would produce a significant drag on the U.S. economy, which has recently showed signs of a sustained recovery.

Obama’s political standing has improved along with the economic numbers. He spent Thursday in the small Northeastern state of New Hampshire, calling for Congress to abolish tax breaks for oil companies.

Obama moved on to New York for four fundraising events Thursday night, preparing for what will surely be one of the most expensive presidential campaigns ever.

At one fundraiser, a supporter openly urged Obama to avoid a war with Iran over its disputed nuclear program. “Nobody has announced a war,” Obama said. “You’re jumping the gun a little bit.”

Obama has blamed higher gasoline costs on market uncertainty over fears that Israel could launch air strikes against nuclear facilities in Iran, a major oil producer. He also has blamed higher costs on growing demand in China and India.

Republicans have seized on climbing fuel prices to attack the president, with Romney hitting hard during a Thursday visit to the oil-boom state of North Dakota.

The former Massachusetts governor said that Obama has tried to slow oil, gas and coal production. “Far from taking credit, he should be hanging his head and taking a little bit of the blame for what’s going on today,” Romney said.

Obama has argued that the U.S. is producing more oil now than at any time in the last eight years.

Meanwhile, Santorum continues to attack Romney as not conservative enough to satisfy the Republican base.

The former Pennsylvania senator’s increasingly conservative campaign positions, which have focused heavily on social issues like abortion, contraception and women in the workplace, have forced Romney to shift his politics further to the right.