President Obama’s proposal to increase taxes on the rich is “designed to come at me,” GOP presidential contender Mitt Romney told me this morning. In his State of the Union speech Tuesday night, Obama proposed a minimum 30% tax rate on Americans earning more than $1 million a year.

The proposal — known as the “Buffett Tax” after Warren Buffett famously said his secretary pays a higher tax rate than he does — was a key part of the president’s populist push for “fairness” in his speech to the nation.

The plan is “designed to come at me if I’m the nominee,” Mr. Romney said in a taped interview. “If I happen not to be the nominee, he’ll still take the 99-versus-one attack. He’s really trying to divide America.”

Mr. Romney, who gave a glimpse inside his personal fortune on Tuesday by releasing his U.S. tax returns, paid an effective tax rate of 13.9% in 2010 and expects to pay a 15.4% effective rate when he files his return for 2011.

Those rates are far below the top income tax rate on wages, which is 35%, because the U.S. tax code favors capital gains and other investment income by taxing them at 15%.

“The question is whether we’re going to eliminate the capital gains tax break,” Mr. Romney said. “So if you say we’re going to raise that dramatically, you’re going to choke off a lot of the capital that goes into creating new enterprises and creating jobs. It’s the wrong way to go.”

Mr. Romney said Republicans are not all about the rich. “I’m fighting to help middle class Americans get better jobs and better incomes. People who have been successful understand the path to success — we want everyone to enjoy success in America.”