Over the past 20 days, Clinton's been averaging about 48.1 percent in the polls. Obama was averaging 47.5 percent during the same period.

How can that be? How can unpopular Clinton be doing as well as fairly-popular Obama? (In October 2012, our poll had Obama's approval rating at 51 percent.) Simple. Donald Trump is doing far worse right now than Mitt Romney was. Romney averaged 47 percent over the most recent period; Trump's averaging 42.3 percent.

Trump's numbers look more like those of John McCain in 2008. During that same 20-day period, McCain averaged 43.2 percent.

But Clinton's doing slightly worse than Obama did that year. (He averaged 49.4 percent from 36 to 17 days before the election that year.)

In other words, Clinton's support is somewhere between Obama's 2008 blowout and his polling in 2012 — which was a bit lower than the actual result. Trump's on par with the 2008 Republican nominee, who lost by more votes than any candidate since Walter Mondale was demolished in 1984. That's where the Clinton favorability numbers are apparent: She should be winning by Obama-2008 numbers, if Trump's losing by McCain-2008 numbers.

Trump's campaign manager, Kellyanne Conway, clearly sees this as an opportunity for Trump. “I am mystified as to why she can't get to those 52, 53 percent numbers in some of these states,” Conway said on CNN last week. The implication is that voters wavering on both candidates will swing to Trump at the end.

Probably not. Trump's unfavorable numbers in our most recent poll had him viewed negatively by two-thirds of registered voters, 53 percent of them strongly. It seems unlikely that voters skeptical of Clinton at this point will choose instead to vote for someone they like less.