Over the course of a very expensive midterm election, Senate Democrats used a number of outside groups to shore up vulnerable incumbents. Federal Election Commission disclosures show that many of these groups relied on SKDKnickerbocker, a Democratic consulting firm, to produce the advertisements that flooded swing states this year.

SKDKnickerbocker, according to multiple reports, was also retained by TransCanada to build support for the Keystone XL pipeline.

The firm, run by veteran Democratic consultants including Anita Dunn and Hilary Rosen, produced advertising for Senate Majority PAC, WomenVote!, Walsh for Montana, and Patriot Majority USA, the highest spending dark money group supporting Democrats this year.

Senate Democrats may now take up a vote to force approval of TransCanada’s Keystone XL pipeline, according to Bloomberg News. The effort has been billed as a maneuver to create political support for Senator Mary Landrieu’s (D-LA) run-off election in December.

The Keystone XL is a pipeline to connect Canadian tar sand oil in Alberta to gulf coast refineries that are designed to process heavy crude for foreign export. Since the pipeline crosses international borders, it requires State Department approval. The ultimate decision has been delayed by President Barack Obama.

A recent study shows that approval of the pipeline, which would eventually ship 830,000 barrels a day, would increase emissions by 100 million to 110 million metric tons a year. As The Guardian’s John Abrams noted, Keystone XL-related carbon emissions would be roughly equivalent to adding pollution from approximately 40 million cars or 55 coal plants.