Oil and Gas influences are worth millions during election campaigns.

Oil & Gas influences 

"This industry, which includes multinational and independent oil and gas producers and refiners, natural gas pipeline companies, gasoline service stations and fuel oil dealers, has long enjoyed a history of strong influence in Washington. Individuals and political action committees affiliated with oil and gas companies have donated $238.7 million to candidates and parties since the 1990 election cycle.."
Obama, "received $884,000 from the oil and gas industry during the 2008 campaign, more than any other lawmaker except his Republican opponent, Sen. John McCain (R-Ariz.)."

Oil & Gas: Background -OpenSecrets.org