Though publicly traded corporations have mostly shied away from new super PACs, one California energy giant is bucking the tide with a $2.5 million donation to a Republican group, new records show.

Chevron Corp. donated the money on Oct. 7 to the Congressional Leadership Fund, a super PAC focused on House races with close ties to Speaker John Boehner (R-Ohio).  The gift appears to be the largest contribution from a publicly traded corporation to a political group since the Supreme Court ruled in 2010 that companies could spend unlimited money on elections.

"Chevron exercises its right to participate in the political process through various contributions," the Concord, Calif.-based oil and gas firm said in a statement Friday. "All of our political contributions are fully disclosed. We support political initiatives and candidates committed to economic development, creating affordable energy, strengthening American businesses, and delivering good government."

The amount dwarfs the $1.2 million that Chevron's political-action committee and its employees have given to federal candidates, primarily to Republicans such as Boehner and presidential nominee Mitt Romney, according to the Center for Responsive Politics. The firm has also spent nearly $15 million on Washington lobbying since the start of 2011. 

In Citizens United v. Federal Election Commission and subsequent rulings, the courts have upended the campaign finance system by making it easier for corporations, unions and wealthy individuals to spend money directly on elections. The loosened regulations have led to a frenzy of spending by outside groups, particularly on the right.

But until now, major companies traded on the New York Stock Exchange or other markets have acted cautiously, fearing the kind of blowback that Target Corp. received in 2010 for helping pay for television ads on behalf of a Republican candidate opposed to gay marriage. Donations to conservative super PACs remain dominated by billionaires or closely held private firms, records show

The $2.5 million from Chevron made up the bulk of the $3.1 million raised by the Congressional Leadership Fund from Oct. 1 to Oct. 17, according to an FEC disclosure filed Thursday. The super PAC and its affiliate, the American Action Network, have said they plan to spend more than $20 million this cycle backing House Republican candidates, who tend to oppose efforts to close tax loopholes for oil companies as well as energy industry regulations. 

Rep. Steve Israel (D-N.Y.), chairman of the Democratic Congressional Campaign Committee, said the Chevron donation "may be the biggest political payoff in history."

"House Republicans protected taxpayer subsidies for Big Oil companies making record profits and now they're getting rewarded," Israel said in a statement.