With energy and the environment emerging as hot button topics this election year, two environment-focused advocacy groups are spending heavily in competitive House and Senate races in Colorado.

The League of Conservation Voters is coming out strongly for Democrat Mark Udall in his run for the seat of retiring U.S. Sen. Wayne Allard (R-Loveland). The organization has sunk more than $565,000 into two television advertisements slamming Udall’s Republican opponent, former U.S. Rep. Bob Schaffer.

Earlier this week, Defenders of Wildlife PAC began airing two television advertisements targeting U.S. Rep. Marilyn Musgrave, who is engaged in a competitive race with Democrat Betsy Markey. The organization has purchased about $200,000 in television airtime and spent about $12,000 to produce the ads.

The Colorado push is part of a broader effort on the part of the League of Conservation Voters, Defenders of Wildlife PAC and the Sierra Club to target competitive House and Senate races in Colorado, New Mexico, and New Hampshire. The plan was initially announced this spring.

As the battle for the Senate took shape, the Defenders of Wildlife PAC focused its efforts in the New Mexico senate primary while the League of Conservation Voters has zeroed in on the Rocky Mountain state. Prior to airing its television advertisements against Schaeffer the organization named Schaffer to its “Dirty Dozen” list, saying the congressman had taken contributions from the oil and gas industry and had voted against developing alternative fuel vehicles.

“Colorado is a key race,” said Josh McNeil, a spokesman for the League of Conservation Voters. “Bob Schaffer was one of the worst congressmen when it came to energy and environmental issues and Mark Udall has been a real champion.”

The Defenders of Wildlife PAC, meanwhile, says that Musgrave has voted to give tax breaks to oil companies. Musgrave, who assumed Schaffer’s office after he retired in 2002, occupies a mainly rural district in eastern and northern Colorado, which includes the cities of Fort Collins, Loveland and Greeley, that is largely conservative. But the district also has an independent streak and the environment is a top concern.

Republicans say that Colorado voters will identify the environmental groups as too liberal for their tastes.

“Extreme liberal groups, such as the League of Conservation voters, are trying to mislead voters and buy the election for Boulder liberal Mark Udall,” said John Randall, a spokesman for the National Republican Senatorial Committee.