The Wall Street Journal's Jonathan Weisman looks at Mitt Romney's implementation of carbon caps in Massachusetts. As the headline notes, this policy could add to the other reasons that conservatives have questions about Mitt Romney's record as governor of Massachusetts.

Republican presidential front-runner Mitt Romney, whose health-care record as governor of Massachusetts has left him struggling to win the support of conservative voters, now faces another point of vulnerability: his environmental record.

Mr. Romney joined activists outside an aging, coal-fired plant in 2003 to show his commitment to the emissions caps. "I will not create jobs or hold jobs that kill people, and that plant, that plant kills people," he said.

On Dec. 7, 2005, the Romney administration unveiled the final orders. "These carbon emission limits will provide real and immediate progress in the battle to improve our environment," then-Gov. Romney said in a press release touting Massachusetts as "the first and only state to set CO2 emissions limits on power plants."