Note: This story has been updated.

As news reports highlight the millions of dollars flowing from corporations and individuals into this year’s presidential election campaigns, money also continues to have an influence on members of Congress. Of 36 U.S. Senators who rank the oil and gas industry among their top 10 contributing industry groups, 31 sponsored or co-sponsored a bill earlier this week to try to push through the controversial Keystone XL oil pipeline.

MapLight, a nonprofit research group, released that and other figures this week showing campaign contributions to Senators from individuals and organizations connected to the oil and gas industry, made between July 1, 2005, and June 30, 2011.

In a recent two-year time frame, contributions to current members of the House of Representatives from individuals and PACs connected to the oil and gas industry have totaled nearly $12 million, MapLight said.

The number one contributor to members of both the House and Senate was Koch Industries, Inc., with over $1 million donated to House members and $742,000 given to Senators. Exxon Mobil was second, with $961,000 and $676,000; followed by Chevron Corp, with $379,000 and $614,000.

Koch general counsel Mark Holden said his company’s stance on the pipeline project remains the same as stated on the Koch Industries webpage, kochfacts.com, which says, “Koch Industries has no financial stake in the Keystone pipeline and we are not party to its design or construction. We are not a proposed shipper or customer of oil delivered by this pipeline. We have taken no position on the legislative proposal at issue before Congress and we are not cited in any way in that legislation.”

MapLight said 19 of the top 20 recipients [XLS] of campaign contributions connected to the oil and gas industry signed on to co-sponsor the Keystone bill. The lone exception was Democrat Mary Landrieu of Louisiana, who received a total of $424,700 from oil and gas interests.

Republican Senator John Hoeven of North Dakota, along with 44 co-sponsors, introduced the bill Monday. Hoeven received $251,789 in contributions from the industry, which ranks as his number one contributor.

The leading individual recipient of the industry’s contributions is Republican Senator John McCain of Arizona, who took in nearly $2.5 million from oil and gas interests. He is one of the bill’s co-sponsors.

The legislation would grant Congress the authority to approve the proposed 1,700-mile pipeline that would transport oil from Alberta, Canada, to the Texas Gulf Coast.

President Barack Obama temporarily rejected the Keystone construction project when Congress forced him to make a quick decision by placing language in the payroll tax law requiring his verdict.

The pipeline is supported by the American Petroleum Institute, the Association of Oil Pipe Lines, the Consumer Energy Alliance, the Independent Petroleum Association of America, the Industrial Energy Consumers of America, and the National Petrochemical & Refiners Association, among others.

A number of environmental groups, also often big political contributors, oppose the Keystone project.

Even if the bill passes, how the legislators expect to avoid a presidential veto is an unanswered question.

The pipeline controversy is playing out at a time of increased scrutiny of corporate contributions to politicians, thanks to the U.S. Supreme Court’s decision two years ago in the Citizens United case, allowing corporations to make unlimited donations to political campaigns.

On Thursday, The New York Times ran a page-one story on donations to the ongoing presidential race based on this week’s required filings with the Federal Election Commission.

The story focused on “not just the scale of donations from corporations and unions but also the secrecy surrounding ‘super PACs’ seeking to influence the presidential race.’ The newspaper explained that by donating to certain nonprofit groups, corporations and others can keep their identities a secret.