As President Obama was speaking at a rally in west Denver, Mitt Romney made a surprise appearance at a Conservative Political Action Committee, or CPAC鈥�

Why do nearly half of U.S families pay no federal income taxes? Low income and special programs for the elderly, the working poor and families with children.

Yes, about half of Americans don't pay income taxes. But experts say few of those are shirking their responsibilities 鈥� and most pay many other types of taxes. Meanwhile, the GOP nominee has mixed some figures to come up with his conclusions, fact checkers say.

With the first presidential debate now behind them, President Obama and his Republican challenger Mitt Romney are back on the campaign trail.Both are鈥�