Ezra Klein of the Washington Post responds to Romney’s remarks:

“83 percent of those not paying federal income taxes are either working and paying payroll taxes or they’re elderly and Romney is promising to protect their benefits. The remainder, by and large, aren’t paying federal income or payroll taxes because they’re unemployed.”

And why don’t many working people end up owing Federal income tax?

“Part of the reason so many Americans don’t pay federal income taxes is that Republicans have passed a series of very large tax cuts that wiped out the income-tax liability for many Americans. That’s why, when you look at graphs of the percent of Americans who don’t pay income taxes, you see huge jumps after Ronald Reagan’s 1986 tax reform and George W. Bush’s 2001 and 2003 tax cuts. So whenever you hear that half of Americans don’t pay federal income taxes, remember: Ronald Reagan and George W. Bush helped build that.”

Klein points out that some of the tax cuts for lower income people were adopted to make tax cuts for higher income people more politically acceptable. Now, however, the Republicans are arguing that people who don’t owe federal income tax are parasites who don’t deserve government benefits:

“Republicans have become outraged over the predictable effect of tax cuts they passed and are using that outrage as the justification for an agenda that further cuts taxes on the rich and pays for it by cutting social services for the non-rich.”

http://www.washingtonpost.com/blogs/ezra-klein/wp/2012/09/17/romneys-theory-of-the-taker-class-and-why-it-matters/