WASHINGTON - The price of oil is spiking, and Minnesota motorists are buying gas now at nearly $4 a gallon.

With the summer driving season close at hand, and a presidential election right behind, lawmakers in Washington are scrambling for answers. Republicans in Congress have renewed their calls for more domestic oil drilling and the speedy approval of the controversial Keystone XL pipeline, which would carry oil from Canada to refineries across the United States.

But Minnesota Sens. Amy Klobuchar and Al Franken, both Democrats, say they have an additional solution: Clamp down on oil speculators.

Klobuchar and Franken have just introduced a long-shot bill to limit "excessive speculation." The term, which has so far eluded a precise definition, re-opens a volatile election-year debate about the true causes of rising gas prices.

Energy traders, analysts and oil industry lobbyists all are pushing back against the notion that speculation is to blame. They say there is no proof that speculative investment is driving up prices on the global oil market, which has been rocked by rising Middle East tensions, economic sanctions against Iran, and the threat of another Israeli war.

But Klobuchar and Franken, joining with Sen. Bernie Sanders, I-Vt., the lead author of the legislation, say oil speculators now make up more than 80 percent of the energy futures market, allowing them to influence the global price.

They cite recently published estimates that suggest speculation adds roughly 56 cents per gallon at the pump. "The American people shouldn't have to be held hostage by Wall Street speculators day after day," Klobuchar said Wednesday at the Senate rollout for the bill.

"This is something that's hurting Americans in their pocket books," Franken said. "It's hurting Minnesotans."

Some industry analysts say that investors injecting money into the market actually helps absorb risk and insulates consumers from price swings caused by geopolitical events and the vagaries of supply and demand.

"If you take the money that speculators put into the market out of the market, then that money either has to come from the producer or the consumer, and that means higher prices in the long run," said Kevin Book of ClearView Energy Partners, an independent research and consulting firm.

The bill's authors say data show that supplies of crude oil and gasoline are higher this month than they were in March 2009, when the national average price for a gallon of regular unleaded gasoline was $1.94. Meanwhile, they say, U.S. demand for gasoline is lower than five years ago.

"The issue is not, in my view, supply and demand," Sanders said. "What we're dealing with is excessive speculation driving up prices." Gasoline prices jumped a nationwide average of 1.7 cents per gallon this week, even amid news that U.S. fuel demand declined and manufacturing has slowed in Europe and China, where demand had been growing in recent years.

Even if Klobuchar and Franken succeed, changes to oil and gasoline policy can take years to filter down and affect pump prices. Previous attempts to limit oil speculation in 2010 are still bogged down in bureaucratic wrangling and court battles.

Also, critics note, the government has yet to spell out what "excessive" speculation is. In fact, so little definitive data exist that the bill being sponsored by Klobuchar and Franken cites a recent Forbes article extrapolating from a Goldman Sachs report as evidence for a 56-cent-a-gallon speculator "premium."

The bill, which is unlikely to get traction in the Republican-led House, calls on the U.S. Commodity Futures Trading Commission (CFTC) to establish emergency limits on speculators' shares of investments in future oil prices. Theoretically, that would curb their ability to artificially drive prices higher.

Sanders and other bill backers complain of tepid action by President Obama, despite the administration's move last year to form a task force looking into potential oil and gas price fraud, market manipulation and speculators' role.

Former CFTC trading and marketing director Michael Greenberger says speculators who have no interests in production or end use have hijacked the oil and gas futures market in a way that makes them rich but distorts prices for farmers, airlines and others who buy futures contracts as a hedge against rising oil prices.

Greenberger welcomes Franken's and Klobuchar's attempts to force the agency to use its emergency powers to temporarily curb speculators.

Besides limiting investments by speculators, the CFTC's emergency powers also would allow the agency to increase the amounts of money that speculators must provide up front to buy futures. Traditionally, speculators have been allowed to buy futures contracts with almost no money down.

"I applaud their efforts," Greenberger said. "They and the other senators involved in this are reaching out to do what they can."

Others see it as risky. "I don't think speculation has caused a drastic increase in the price of gas," said Felix Shipkevich, a New York lawyer specializing in CFTC regulations. "A lot of things go into what a barrel of oil costs."

Shipkevich said the effectiveness of position limits in controlling fuel prices lacks "empirical evidence." Cracking down only in the U.S. futures market is not necessarily a panacea, he added, because new restrictions will only drive business overseas.

"Singapore is already welcoming [American traders]," Shipkevich said. "We live in a global economy."

The legislation cannot stop that migration. But Shipkevich believes politicians who blast oil speculators and the CFTC can score points with angry voters. "These are elected officials," he said. "They're looking for someone to blame."

Kevin Diaz and Jim Spencer are correspondents in the Star Tribune Washington Bureau.