I’d urge a little bit of caution here, given that swings in enthusiasm can be transient and can sometimes exaggerate the underlying change in voter sentiment. Our polls-only forecast has Clinton up by about 7 percentage points instead of by double digits — and our polls-plus forecast would still bet on the race tightening slightly.
But you can easily see how the worst-case scenario is firmly on the table for Trump and Republican down-ballot candidates, where the bottom falls out from GOP turnout. Consider:
+ Trump is getting only about 80 percent of the Republican vote, whereas candidates typically finish at about 90 percent of their party’s vote or above.
+ Furthermore, the Republicans missing from Trump’s column tend to be high-education, high-income voters, who typically also have a high propensity to vote.
+ Voters are increasingly convinced that Clinton will win the election, and turnout can be lower in lopsided elections. (Although, this presents risks to both candidates: complacency on the part of Democrats, despondency on the part of Republicans.)
+ Republicans and Trump have a substantial ground game deficit, with Clinton and Democrats holding a nearly 4-1 advantage in paid staffers.
+ Trump’s rhetoric that the election is rigged could discourage turnout among his own voters.
+ Trump’s base is relatively small, especially if he underperforms among college-educated Republicans.
The nightmare scenario for the GOP is that high-information Republican voters, seeing Trump imploding and not necessarily having been happy with him as their nominee in the first place, feel free to cast a protest vote at the top of the ticket. Meanwhile, lower-information Republican voters don’t turn out at all, given that Trump’s rigging rhetoric could suppress their vote and that Republicans don’t have the field operation to pull them back in. That’s how you could get a Clinton landslide like the one the ABC News poll describes, along with a Democratic Senate and possibly even — although it’s a reach — a Democratic House.