Des Moines (CNN) - Hours before Iowa caucuses, the Ron Paul campaign has launched its sharpest anti-Romney attack ad yet, a one-minute radio spot calling the former Massachusetts governor a "liberal" who has supported government bailouts, healthcare mandates and big government.
The ad was running in Iowa Tuesday morning and afternoon.
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The announcer reads, "Mitt Romney can't fight against Obamacare because he supported the same mandates and government takeovers as governor of Massachusetts. Romney can't stand up against more bailouts because he supported them. He can't lead the charge to shrink the government because he has grown it."
The ad is testimony to Paul's concerns about Romney, who is the frontrunner in recent Iowa polls. The final-day, closing-argument radio spot directly attacks what some perceive as Romney's strength: electability.
"Romney's record is liberal and putting him up against Obama is a recipe for defeat," the announcer reads, "That candidate who can beat Obama is Dr. Ron Paul."
The radio ad also extends a Paul theme, using the word "liberal" to slam his opponents on fiscal policies, including earmarks and spending.
In an interview with CNN's Dana Bash Monday, Paul called opponent Rick Santorum "very liberal".
"He spends too much money," Paul said.
Paul's campaign confirmed placing the Tuesday radio ad.
– Dana Bash contributed to this report.
– Follow Lisa Desjardins on Twitter: @LisaDCNN