Pollsters show Clinton receiving varying levels of support from Sanders voters, but CNN, Fox News,2 Marist and YouGov all show Clinton’s margin over Trump among these voters shrinking when third-party candidates are presented as options. On average, Clinton loses 12 percentage points off her margin over Trump among Sanders backers — identical to the change I calculated before both conventions took place. Clinton is below 70 percent among Sanders backers in all four polls and wins an average of just 63 percent when third-party candidates are included. That’s about as well as Trump is doing among well-educated, moderate Republicans — the wing of the GOP least likely to back him. In other words, the Democratic convention seems to have been somewhat of a failure in convincing Sanders voters who oppose Trump to consolidate behind Clinton rather than Johnson or Stein.
Of course, Clinton has already won over some Sanders holdouts, and she may just steadily pick up more of their votes as the campaign progresses. Additionally, Johnson’s support in national polls — in both our polls-only and polls-plus forecasts — has been trending downwards slightly.3 That suggests voters may be moving away from third-party options, which is in keeping with the history of third-party candidates fading as the election nears.