Democrats said today that they will push the “Buffett Rule” targeting millionaires all year long and ripped House Majority Leader Eric Cantor’s (R-Va.) proposed 20 percent tax cut for small-business owners as another giveaway to the wealthy.

“We have a great opportunity when we return to Washington to reverse an unfairness in the tax code that virtually every American knows about,” Sen. Sheldon Whitehouse (D-R.I.) said. The Buffett Rule bill, which Whitehouse is sponsoring in the Senate, would impose a minimum tax rate on millionaires that he said would raise $50 billion or more during the coming decade.

The measure is aimed at implementing President Barack Obama’s principle that people who make more than $1 million a year should pay at least as high a percentage of their income in taxes as the middle class. It’s named after billionaire investor Warren Buffett, who proposed it after finding his secretary pays a higher tax rate than he does.

“It makes no sense … to have a hard-working Rhode Islander to be paying more than a hedge fund billionaire,” Whitehouse said.

Senate Democratic Conference Vice Chairman Charles Schumer noted that Senate Democrats pushed to draft legislation implementing the principle after the White House merely named it as a principle for tax reform.

“Many of us in the Senate said, ‘Why wait? Let’s draft it as stand-alone legislation and vote on it,’” the New Yorker said.

Schumer said that even if the Buffett Rule didn’t raise any money, fairness would still be an issue.

And the Democrats made it clear that they see the issue as a winner in the fall elections.

“This is going to be a defining issue in 2012,” said Rep. Tammy Baldwin (D-Wis.), who is running for Senate.

“We’re going to keep pushing this issue all year long,” Schumer said. The Buffett Rule, he said, has put the GOP “on the defensive on their signature issue, taxes.”

Schumer said that if the Bush tax cuts are extended as the GOP wishes, the Buffett Rule would raise about $160 billion.

Schumer torched Cantor’s small-business tax cut proposal minutes before another Cantor-led effort, the JOBS Act, was due to be signed in a Rose Garden ceremony.

Schumer said Cantor’s proposal decreases taxes on sports figures, financial leaders and multimillionaires “who might not create a single job.”

Schumer said the idea of just reducing taxes regardless of whether they are productive or adding workers “makes no sense to us.”

The Democrats’ small-business tax cut, which is modeled on Obama’s proposal from last year, would reward companies for growing their payrolls or investing in new facilities and equipment.

Cantor has defended his proposed tax cut, and in particular his decision not to carve out exceptions for industries such as pornography producers, financial firms, sports teams and the like, by saying that Congress doesn’t do that for the rest of the tax code.

As for talk that GOP presidential frontrunner Mitt Romney might pick House Budget Chairman Paul Ryan (R-Wis.) as his running mate, Schumer dismissed that scenario. “He’s going to have to move much more to the center,” Schumer said of Romney. Democrats contend Ryan’s budget blueprint, which recently passed the House, panders to the tea party faction on the GOP and would endanger federal programs, including entitlements such as Medicare and Medicaid, by requiring steep spending cuts.