The White House said Tuesday that the president will argue that the American tax code is "increasingly rigged in favor of the wealthiest Americans" and push Senate Republicans on why they do not support the proposed "Buffett Rule" during a speech in Florida Tuesday afternoon.

The president has signaled that the proposal — which would raise the effective tax rate on millionaire and billionaire investment income to at least 30 percent — will be a cornerstone of his reelection bid.

White House press secretary Jay Carney said the president is expected to hammer the theme of "fairness," hoping to frame Republican opposition to the bill as protection of a tax code "increasingly rigged in favor of the wealthiest Americans."

Those comments directly mirrored those made on Tuesday morning by senior campaign strategist David Axelrod, who decried the tax code as “rigged in favor of the very wealthy" during an interview with MSNBC.

"We have a tax system that is rigged against the average person, rigged in favor of the very wealthy, and we need to fix that. This Buffett Rule will address that, and most Americans, I think, would agree with it," Axelrod said.

The Senate is expected to vote on the Buffett Rule proposal next week, although the legislation will likely fall short of the 60 votes it needs to pass. But the White House clearly sees political opportunity in the vote, telling reporters that it was up to Republicans in the Senate to explain their vote.

"We certainly understand that it's a challenge to persuade Republicans in the Senate ... in this case to listen to their constituents who overwhelmingly support the idea of tax fairness," Carney said.

But the White House press said the bill had some life, despite admittedly long odds.

"It may be an uphill battle but it's not an impossible battle because their own constituents are urging them to do so," Carney said.

Obama will deliver his Buffett Rule speech at Florida Atlantic University, sandwiched between reelection fundraisers in southern Florida.