In 1986, Wirth ran for the U.S. Senate and on his party's nomination unopposed to replace Sen. Gary Hart. The general election was more difficult than expected, and he defeated fellow U.S. Representative Ken Kramer by a narrow margin. In the Senate, he focused on environmental issues, particularly global climate change and population stabilization. In 1988, he organized the historic Hansen hearings on climate change. Wirth in an interview to PBS, admitted to staging the hearing by intentionally scheduling it on the historically hottest day of the summer and opening the windows to the hearing room the night before so the air conditioning would not be working.[3] With his close friend, the late Senator John Heinz (R-PA), he authored "Project 88", outlining the groundbreaking "Cap and Trade" idea which became law in the Clean Air Act Amendments of 1990. He authored the far-reaching Colorado Wilderness Bill which became law in 1993, and with Senator Alan Simpson (R-WY) he authored major legislation focused on population stabilization. Wirth also organized the Senate Task Force on the Expansion of Major League Baseball, which became a major factor in the awarding of a new expansion franchise to Denver. He chose not to run for re-election in 1992, citing in a front page cover story in the Sunday New York Times Magazine (August 9, 1992), frustration with the ever-increasing role of money in politics to the exclusion of focus on public policy.

https://en.wikipedia.org/wiki/Tim_Wirth

and as usual with wikipedia the real painful facts are in the discussion