The campaign said it will air a 60-second ad called "Three of a Kind" that it released earlier this week that attacks each of the remaining candidates in the GOP field. That notably includes a hit on Mitt Romney as "flip-flopper who has been on all sides," Paul's first attack on the Republican front-runner since the Iowa caucuses.

Rick Santorum is dismissed as a "counterfeit conservative," while Newt Gingrich is labeled a "serial hypocrite."

“By airing ‘Three of a Kind’ in Idaho, we’re demonstrating Ron Paul’s commitment to Idahoans who have welcomed Paul and other candidates to their state far earlier than they have in prior presidential election cycles,” said Paul spokesman Jesse Benton in a statement. “Delegate-rich Idaho is fertile ground for a competitive showing by Dr. Paul and we’re working hard to ensure that the Gem State proves to be an integral part of our delegate-attainment strategy to win the nomination."

"One is a serial hypocrite who lobbied for Freddie Mac before the housing crisis and for the indiviual mandate before ObamaCare," the ad's narrator says. "Another, a counterfeit conservative who opposes 'right to work,' massively increased spending and funded Planned Parenthood. Finally, a flip-flopper who has been on all sides, supported TARP bailouts and provided the blueprint for ObamaCare.Three men, one vision: More big government, more mandates, less freedom."

The ad is already airing in Washington state. The Paul campaign has also bought airtime in Vermont, but is playing a shorter 30-second spot that heralds the congressman's record.

Idaho will award 32 delegates to the GOP convention Tuesday — far less than states like Ohio and Tennessee — but still more than hotly contested early primaries like Iowa, New Hampshire, Nevada and Michigan.