Republicans in the North Carolina state legislature successfully overrode a veto to its bill allowing the fracking of natural gas, after a Democrat opponent absent-mindedly pushed the wrong button.
State representative Becky Carney said that while sitting at her desk during Monday night's vote she plumped erroneously for the green "yes" button, only realising afterwards that she had meant to select the red "no".
The resulting 72-47 vote gave Republicans the majority they needed to overrule Governor Beverly Perdue's veto of a measure that could advance the use of fracking in the state.
Carney's slip followed a marathon debate in the state legislature over the controversial mining technique opposed by many environmentalists.
It came to a vote just after 11pm.
Carney realised her mistake soon after making it, but Republicans in the House refused to allow her to retract her "yes" vote. The chamber's rules prevent members from changing a vote if it affects the outcome.
Speaking to the Charlotte Observer on Tuesday, Carney put her hands up to the error.
"It was a huge mistake. I take full responsibility," she told the newspaper.
