Yes, Biden Has A Big Lead, But It's Probably Not 15 Points (538.com)

[Drunken Irishman]

3. Agreed. It's unlikely in today's environment that a candidate will ever win by 15 points nationally.

As a reminder: Obama, in a Democratic year, with massive Democratic enthusiasm and a very unpopular Republican president (granted, one who wasn't running - but his party was still in the election and McCain was every much a Bush Republican by that point) "only" won the popular vote by roughly seven-points nationally.

Here's the popular vote margin going back to the 1976 presidential election (for the winner, obviously):

1976: +2.1
1980: +9.7
1984: +18.2
1988: +7.8
1992: +5.6
1996: +8.5
2000: -0.5
2004: +2.4
2008: +7.2
2012: +3.9
2016: -2.1

Only once, 1984, did a candidate win the popular vote by ten-plus points. That was Reagan's landslide year.

The second closest was Reagan's win in 1980, which you can round to 10. After that, it was Clinton's reelection in 1996.

Hard to imagine Biden is really up 15.

But if he's up 8-11, that puts him at a level not seen since at least 1996.