Mrs. Clinton may also get an assist from one Democrat who has been largely quiet about the race, but can testify to the importance of resisting the third-party temptation: former Vice President Al Gore. Her staff has had conversations with aides to Mr. Gore about bringing him onto the campaign trail to emphasize the importance of supporting Mrs. Clinton if they want to make progress on combating climate change.

“I can assure you from personal experience that every vote counts,” Mr. Gore wrote in an email to The New York Times on Thursday, after a new CBS/New York Times poll showed Mrs. Clinton and Mr. Trump virtually tied. “The stakes are high for so many Americans. So I will vote for Hillary Clinton and I strongly encourage others to vote for her as well.”

...

“You’re going to end up with Nader electing Bush again if they vote that way,” warned Mr. Daley, who was the campaign chairman for Mr. Gore in 2000 when he lost Florida, and the presidency, in part because liberals supported Mr. Nader, the Green Party nominee that year.

Some Clinton supporters expressed frustration that an interview Mr. Gore gave last month to a liberal website warning about the perils of straying from the major party candidates did not draw more attention.

“I would also urge them to look carefully, as I know they have, at the consequences of going in another direction for the third or fourth alternative,” Mr. Gore told ThinkProgress.

As a side note, can we talk about the NYT's crutch of reporting about "some [Clinton/Sanders supporters]/Democrats"?