Pundits across the political spectrum have asked why the president decided to punt on debt reduction ideas from his own Bowles-Simpson commission. (Former Republican U.S. Sen. Alan Simpson shared his theory during a recent joint appearance with retired UNC system president Erskine Bowles at Duke University.)

Writing in the latest National Review, American Enterprise institute blogger James Pethokoukis offers his own ideas. The key for Pethokoukis is President Obama’s statement during his latest State of the Union address that “If you make more than $1 million a year, you should not pay less than 30 percent in taxes.”

Obama’s specific terms and conditions are crucial. He could have said merely that millionaires should not pay a lower tax rate than middle-income Americans and left it at that. Instead, he specified a particular tax rate and made it a minimum requirement. As it happens, that floor of 30 percent about matches the average effective tax rate of the top 1 percent of American households. ([Warren] Buffett pays around a 17 percent rate because most of his income is from investments and is taxed at a preferential 15 percent rate. Same goes for Republican presidential contender Mitt Romney.) The Bowles-Simpson proposal went in completely the other direction. It recommended cutting top marginal rates across the board, specifically stating that “the top rate must not exceed 29 percent.” Indeed, one Bowles-Simpson scenario would have slashed the top marginal rate to 23 percent — the lowest since 1916. Those cuts in marginal rates would have been combined with the elimination of most tax breaks, making Bowles-Simpson a large net tax increase. But whereas Obama would create a floor for tax rates with the Buffett rule, Bowles-Simpson would have created a ceiling. …

… The Buffett rule is a direct outgrowth of the Democrats’ rejection of the Bowles-Simpson premise that federal spending as a share of GDP should be limited to 21 percent of the nation’s economic output, which is about its historical average. Liberals argue that the aging of the population and the need for new government “investments” will require federal spending to be much higher in the future than it has been since World War II.

Pethokoukis goes on to note that “many left-of-center policymakers” support economic research suggesting top marginal tax rates “should revert to at least 70 percent, where they were when Ronald Reagan took office in 1981, and maybe as high as 80 or 90 percent.”