While campaigning in south St. Louis county, Todd Akin (R-MO) explained how Claire McCaskill (D-MO) supported cap and trade. While it's true she did not vote for the cap and trade legislation introduced in 2009, she did vote for it in 2008.
More recently, she voted to grant authority to the EPA to regulate carbon emissions. That effectively allows the EPA to implement cap and trade and other policies that will increase the cost of energy. As Americans for Tax Reform wrote the other day:
She supported the Administration’s efforts to classify carbon dioxide as a pollutant, and voted over and over against amendments to block the EPA from regulating CO2 and other greenhouse gases. Even the Missouri AFL-CIO president said these EPA regulations “will both threaten jobs and increase costs on energy consumers in Missouri.” Bear in mind, humans exhale carbon dioxide. From an economic standpoint, this policy is devastating – St. Louis’ Meramec power plant is older, and is likely to close because of these policies.