Supporters of revising the corporate tax system counter that half a loaf is better than none.

“If you can’t do everything, do business tax reform,” advised Treasury Secretary Jack Lew on Tuesday at a Wall Street Journal conference, responding to the Baucus proposal. “Have our statutory rate not be something that drives business out but that attracts business to the United States,” he added. “Deal with the disparity between U.S. and international tax rates, eliminate some of the tax provisions that skew investment decisions.”

Mr. Baucus was circumspect.

“Let’s get reaction to the draft and see what happens,” he said.

Under the current system, all corporate earnings are supposed to be taxed at 35 percent. In reality, much business income is not. Profits abroad are taxed only when brought to the United States, so much of it never comes home. And companies can move to low-tax havens, then sell into the American market.

Mr. Baucus proposed two alternatives. In both, all earnings from foreign-subsidiary sales into the United States would be taxed immediately at the American corporate tax rate.

Under one, foreign subsidiaries of American companies would not have any of their foreign earnings from non-American sales taxed if they paid 80 percent of their American tax burden to the country in which they were based. If they paid less than 80 percent, say, 75 percent, the other 5 percent would be taxed at the rate in the United States.

The other proposal would exempt 40 percent of active foreign-market income. The other 60 percent would be taxed at the American corporate rate, minus credits for taxes paid abroad.

The proposal does not set a new corporate tax rate, but Finance Committee aides said the proposal should be able to bring the rate below 30 percent.