Clinton's lead is looking a lot like Obama's in 2008

Democratic presidential candidate Hillary Clinton smiles as she speaks to members of the media while aboard her campaign plane after the second debate. Photo / AP

After the release of a NBC/Wall Street Journal poll today, RealClearPolitics updated its national polling average to reflect the shift in the presidential race.

That new poll shows Hillary Clinton with a big lead over Donald Trump, some 14 points in the wake of the hot-mic videotape that's undercut Trump's support.

In the absence of other polls showing a similar spread, though, the average shows a more modest 5.8-point gap between the two.

From a historical perspective, it's normal to see movement shortly after the first debate. In 2000 the results shifted back towards George W. Bush after the first debate. In 2012, the race shifted away from Barack Obama.

More importantly, though, the results are steadily moving further towards Clinton. Clinton's lead now (or, actually, as of yesterday, the date of the completion of the NBC/Wall Street Journal poll) is higher than at the same point in any of the other cycles except 2008. That year, with 30 days to go, Obama led John McCain by 5.9 points. Now, Clinton leads Trump by 5.8.

This is a very bad sign for Trump, but not because the comparison between Clinton and Obama will necessarily hold. It's a bad sign for him because he needed the line to move to the left in his direction, not further towards Clinton.

What happened? Well, we can turn to 2008 to explain that, too.

At about the 50-day mark in 2008, the global economy tanked, which helped propel Obama's victory. This year, there was a similar shock. It wasn't Wall Street that crashed, though. It was Trump.