There are significant differences between the two candidaes on tax policy. McCain would like to make the Bush tax cuts of 2001 and 2003 permanent, and has proposed a few more of his own. Obama, by contrast, favors allowing the tax cuts to expire as scheduled for Americans earning more than $250,000 a year. He would raise taxes on capital gains and dividends, but has also promised tax breaks for low and middle-income Americans.McCain's speech to the Small Business Summit yesterday leaves the impression that Obama favors raising taxes on all Americans, across the board. But his words have been carefully parsed. A more literal reading suggests that he could also be talking about some Americans from "every background," not "all Americans." The key issue is how many low and middle-income Americans would be affected by the Obama tax increases.In order to substantiate its claim that large numbers of ordinary Americans will be worse off under the Democrats, the McCain camp points to an Obama proposal to raise tax rates on dividends and capital gains. Obama advisers argue that any tax increases will be offset by credits for lower-income families. They also point out that most middle and low-income families invest in the market through 401 (k) plans that are exempt from capital gains taxes.