New MoveOn.org ad: Mitt Romney supports 'fat cats who won't pay their fair share'

"President Obama’s Buffett Rule would require millionaires and billionaires to pay the same tax rate as the rest of us," the ad says as pictures of overweight cats fly across the screen. "The Romney Rule lets fat cats rig the system, so they pay less and pass on the burden to hardworking Americans like you and me.”

The 30-second ad, uploaded to YouTube Monday to coincide with Tax Day and Monday's Senate vote on the "Buffett Rule," is set to air on Animal Planet during cat-themed shows like "Big Cat Diary," "My Cat From Hell," and "Cats 101."

"Americans who have been playing by the rules are losing because fat cats like Mitt Romney are playing by a completely different rulebook,” Executive Director of MoveOn.org Justin Ruben said in a statement. “President Obama’s Buffett Rule is a basic first step towards asking fat cat millionaires and billionaires to pay their fair share like the rest of us kitties.”

Democrats have been pushing the tax issue for months, but as the general election begins the expected GOP presidential nominee is pushing back. Romney has compared the tax plan as a "new source of division" by calling out the nation's wealthiest, according to CNN.

Trying to label Romney as a "fat cat" himself, MoveOn.org targeted the former Massachusetts governor for his opposition.

“When the wealthiest 1% pay a fair tax rate like the rest of us, it keeps the American Dream alive for everyone," the ad says. "So tell Mitt Romney, kittens are cute. 1% fat cats who won’t pay their fair share? Eh, not so much.”