It's not yet clear what precise form a Buffett rule would take, if it passed. The Obama administration hasn't spelled out a plan in detail. But one Buffett rule proposal, launched by Sen. Sheldon Whitehouse (D) of Rhode Island, would bring in about $47 billion in extra revenue during the next decade, according to Congress's Joint Committee on Taxation. By other estimates, the rule could bring in more revenue than that (as much as $171 billion) or less.
In any case, the rule would fix only a small part of a budget gap that totals $6.7 trillion in Obama's budget outlook for the decade.
Confronting critics who say it wouldn't patch the budget hole, Obama said simply, "I agree," while arguing that it's still right to take steps in a positive direction.
Senator Whitehouse says his bill would "ensure that multimillion-dollar earners pay at least a 30 percent effective tax rate," while preserving a tax-deduction incentive for charitable giving. The Senate measure is not expected to win enough votes to avoid a filibuster.