This article shows how discussions of political statsitics is in the dark ages. Here is the relevant graph:
Both polls, released on Sunday, showed Mr. Trump in worse shape than he had been a month ago… Despite his woes, not all the results of the new polls were heartening for Mrs. Clinton. The Journal-NBC survey found that her lead essentially disappears when candidates from the Green Party and Libertarian Party are included. She essentially tied Mr. Trump, with 39 percent to his 38 percent. Together, third-party candidates grabbed 16 percent of the support.
Actually, that’s even worse news for Trump than polls showing that Clinton has opened up her lead. To understand this, let’s look at the conservative WSJ-NBC News poll mentioned.
That poll has Clinton at 46% and Trump at 43%, a three point lead nationally. This is one of the most conservative two way polls out there as aggregate polling (which includes three way polling) has her ahead by 6.8%, so we can see the understandable Republican bias in a Wall Street Journal poll. But even taking that into account, we see a 11% undecided/non-reporting account so the real question that all the early reporting needs to answer given how well known both candidates are is: which way is are these huge number of non-reporters going to break?
What the three way race shows is a window into these undecideds. It says right now Clinton has the larger number of holdouts than Trump: about ~60% of these people would rather vote for her than Trump, making her lead much bigger than the numbers are showing.
It reminds me when people say stupid things like, “It’s okay to vote for a third party in a blue state” when studies have conclusively shown that the best way to push policies in a direction is with a bigger margin of victory because the more competitive the election, the more moderate the politician’s position irrespective of incumbency or how “fixed” their candidate position seems.
In other words, if Bernie Sanders really wanted the outcomes he espouses, he’d be endorsing Hillary and pushing hard for a large electoral win, because that, more than anything, would give President Clinton the freedom to move to the left. Instead, he acts in direct opposition to his stated outcomes and pushes her toward the middle.