Republican members of Congress have been pushing Speaker Nancy Pelosi (D., Calif.) to take immediate action on offshore oil drilling, calling for Congress to return to Washington to pass legislation on the matter. Pelosi, however, has vowed not to let the legislation come up for a vote.

Offshore oil drilling offers a boon to big oil companies, which often can be good for a candidate's campaign coffers but may now prove costly at the polls. Just ask freshman republican Representative David Davis of Tennessee who lost his re-election bid in a Republican primary Thursday night.

Davis suffered a narrow defeat: losing by 500 votes out of 51,000 cast. He was upset by Johnson City Mayor Phil Roe in a state where an incumbent congressmember hasn't lost in more than four decades.

The campaign became particularly bitter. Roe's campaign decided on an aggressive strategy tying Davis to big oil companies like

Exxon Mobil

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, accusing Davis of taking money from Political Action Committees (PACs) supporting big oil companies. The attack move paid off for Roe.

Voters chose change in the primary election. Davis is the fourth incumbent Congressman to lose in a primary election this year, which should send shivers through politicians running for re-election this fall.

The primary race in Tennessee may offer some insight into the larger political fight taking place in national politics.

Republicans face incredible pressure in this cycle. Almost 20 Republican congressmembers have retired already. Sen. Ted Stevens (R., Alaska) was indicted last week on charges he lied to federal investigators. And President Bush now has

very low approval ratings

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, with two out of three Americans disapproving of his performance.

Clearly, $4-a-gallon gas has turned petroleum into a large political issue. But it is unclear whether the average American understands the complex issue surrounding inelastic oil markets. Politicians and the media have blamed everyone. Villains include greedy oil nations like Saudi Arabia and Venezuela, nefarious oil speculators or increased demand from developing economies like China and India.

Republican leadership in Congress and the presumptive Republican nominee for president, Sen. John McCain of Arizona, have banked heavily on offshore drilling. Polls over the last few months have shown Americans consider it a viable option to resolve the oil crisis. One poll taken last week by

CNN

found that 69% support offshore drilling. McCain has espoused other gimmicks like the summer gas tax holiday to get voters' attention.

McCain has already taken out aggressive energy ads against Sen. Barack Obama, the presumptive democratic presidential candidate. Several weeks ago, McCain's campaign charged Obama as directly responsible for the high price of gas at the pump. This incendiary claim, even if not entirely true, has helped McCain gain slightly in the polls against Obama.

Democrats disagree strongly with Republicans on the issue of oil. Speaker Pelosi has pointed out that the U.S. Department of Energy analyzed offshore oil wells in both the Arctic (ANWAR) and the Outer Continental Shelf wouldn't produce any petroleum until 2017. Democrats say big oil companies already have 68 million acres under lease -- more than two-thirds of which have yet to be tapped for oil.

Obama has joined congressional Democrats in opposition to drilling. He has supported "use it or lose it" provisions to ensure that oil companies utilize already leased land.

Obama and the Democratic Party have increased their attacks on Republicans for backing Big Oil companies. They have charged McCain leads in taking money from oil company executives and employees in the race, more than $1.1 million. During a town hall meeting in Elkhart, Ind., Obama said:

"So if Senator McCain wants to talk about why Washington is broken, that's a debate I'm happy to have. Because Senator McCain's energy plan reads like an early Christmas list for oil and gas lobbyists. And it's no wonder -- because many of his top advisors are former oil and gas lobbyists."

The final decision, of course, comes down to voter choice. We now know in at least one case in Tennessee they chose change and opposed Big Oil. If that Republican primary is representative of the larger public's political thinking, it could be bad news for Republicans in the fall.