But on the campaign trail, the prospect of using the nation's rainy-day supply is catching on. Last week, Sen. John McCain, the Republican candidate for president, called for the government to stopping adding to the reserve. A week ago at a candidates' debate in Pennsylvania, Sen. Hillary Rodham Clinton (D) said she would not only stop adding to the reserve, but would also release oil to try to drive prices down. Sen. Barack Obama, the other Democratic candidate for president, believes the SPR should be used for short-term supply disruptions, but he does not believe it should be currently tapped, according to Jason Grumet, an adviser on energy to Senator Obama. Like Senator McCain, however, Obama would stop adding to the SPR at these prices, Mr. Grumet says.