The conservative group, Americans for Prosperity, is launching an advertising campaign against Missouri Republican lawmakers who don't support right to work.
Television ads paid for by the group began running in Rep. Kathie Conway's district today.
Conway didn't immediately comment on the matter.
The ads come after Republican House members such as Conway helped defeat a measure that would ban mandatory union fees in Missouri. The measure came 13 votes short of a veto override in the House earlier this month.
The advertisements generally attempt to tie House Republicans who voted against the measure to President Barack Obama, who also opposes right to work. One ad urges voters to call Conway and ask her to support the measure.