In a report published Sunday, The Denver Post said Xcel gave $1 million to help stage the convention, held last week in St. Paul, Minn., about the same time Coleman was supporting a Senate bill that defined nuclear power along with wind and solar power as a renewable-energy resource.
A spokesman for Coleman dismissed any link between Xcel's RNC contribution and his legislative actions, the newspaper said.
"There is absolutely no connection between Senator Coleman's legislative agenda and the financial support that any company or organization made to the 2008 RNC convention," Coleman spokesman Leroy Coleman said.
The controversy illustrates flaws in the current system of raising money for the conventions, Steve Weissman, associate director for policy at the Campaign Finance Institute in Washington, told the Post.
"You can give $1 million, $6 million or as much as you want to the conventions," he said. "These contributions make an enormous impression, and they're clearly related to companies' interests."