Mitt Romney is the only presidential nominee at this stage of the campaign to still be viewed in an unfavorable light by voters, according to a new Pew Research Center poll.

Pew has measured the favorability of both parties' candidates dating back to the 1988 election between Republican George H.W. Bush and Democrat Michael Dukakis. Every candidate has been above water in favorability ratings by September.

In fact, aside from George H.W. Bush's rating running for a second term in office, every candidate has had double-digit net positive favorability ratings by this point.

Here's a look:

Favorability has been an issue that has continued to plague Romney throughout the campaign season. It's why, in the Pew poll, he faces big gaps on questions that ask which candidate "connects well with ordinary Americans."

But favorability, as the chart shows, is not necessarily an absolute predictor of election outcome. In the 2000 race George W. Bush won the election despite facing an 11-point favorability gap against Democrat Al Gore. But Bush was still viewed in a highly favorable light.