Here's one more way to measure Mitt Romney's unpopularity: He's less popular than George W. Bush, the last Republican president who's so unpopular he didn't speak at the Republican National Convention and gave his endorsement of Romney while leaping into an elevator. A Bloomberg poll released this week finds 49 percent of likely voters see Bush unfavorably while 46 percent see him favorably. That beats Romney's results -- 50 percent see him unfavorably and 43 percent view him favorably, as the Dallas Morning News' Tom Benning points out. This poll does not appear to be an outlier in showing Romney's unpopularity.

Pew Research Center reported last week that Romney was the first candidate to have a net negative rating -- more people dislike him than like him -- in September since it began tracking the ratings in 1988. (Pew found Romney's favorability deficit to be slightly smaller than Bloomberg—5 percentage points instead of 7—but still found that 50 percent of registered voters see him unfavorably.) Gallup says Romney is the first presidential candidate to fall in polls after his party's convention, and that his acceptance speech was the most poorly received since Bob Dole in 1996, when the pollster began measuring voter reactions to acceptance speeches.