Republican presidential candidate Rick Santorum is sending out automated phone messages encouraging Michigan Democrats to vote against his rival Mitt Romney in Tuesday's GOP primary.
Romney is calling the phone calls "a dirty trick."
Santorum is shrugging off Romney's criticism, telling Fox News that he is trying to attract the Democratic voters he'll need in a general election campaign.
The "robocall" going around Monday says Democrats should send "a loud message" to Romney by voting for Santorum. The message says it's supported by "hard-working Democratic men and women" and paid for by the Santorum campaign.
Romney tells Fox News that the robocall sounds like it's coming from organized labor and Democrats, and he says the effort is confusing people and deceptive. Romney calls it "a new low" in the campaign.