And not a close fourth, either.

Consider this a capper to Hell Week for Trump in the polls. John wrote up the topline numbers from the McClatchy survey last night but this result is the one that has data nerds buzzing. There’s evidence from elections past that partisan preferences forged by young voters tend to “stick” to some extent as they get older. In other words, if you reached voting age during the New Deal, when America was trending heavily blue, chances are you voted Democratic — and continued to vote Democratic in later years. That being so, neither party wants to get in a deep hole with young voters since they may carry their early preferences with them for decades to come. If that’s true, after two elections in which Obama cleaned up off of young voters plus a third election now in which Trump is polling almost impossibly badly among them, the left may have banked an advantage among a particular age group that’ll persist for several generations of elections.

Trump running fourth behind Clinton, Johnson and Stein among 18-29 year-olds in the Marist poll (h/t @dznyc) pic.twitter.com/IHysoPKSzs

— (((Harry Enten))) (@ForecasterEnten) August 4, 2016

A preposterous outlier? Don’t be so sure. Remember, just last month Pew found Trump trailing Gary Johnson among this same age group. Per McClatchy’s crosstabs, of 40 different demographic subgroups tested (race, age, income, region, and on and on), the only one not directly related to political ideology that views Trump less favorably than young adults is blacks. His favorable rating among them is 5/88, although Republicans are sadly used to losing the black vote nearly unanimously. Among young adults, though, Trump’s rating is a comparable … 13/82. Even Latinos are more favorable to him at 25/73.

Frankly, it’s a testament to how much young voters also dislike Clinton that she’s leading Trump among the 18-29 group by “only” 36 points, 53/17. (Maybe that’ll counteract the “stickiness” of partisan preferences that are being forged right now.) Amazingly, more young adults are voting for Trump (17 percent) than say they view him favorably (13 percent); that can only mean that some who dislike him are backing him anyway because they hate her more. But then, that same effect is helping Hillary much more than it’s helping Trump: When you ask young adults who are voting for her whether they’re voting for her or against Trump, they split 34/62 — the single most lopsided result on that question among any demographic group. Young adults have little use for her, but Trump has made them reluctant Hillary backers. Imagine what sort of margin a likable Democrat like Joe Biden might be putting up against him.

And imagine how far ahead even Clinton, who’s already leading big, might be if she didn’t have Gary Johnson and Jill Stein picking off votes this year:

Why is Johnson (and Stein, for that matter) drawing more from Clinton when he is a former Republican in a year when Republicans are far more likely than Democrats to defect to the third-party candidates?

Young voters. In the Fox News poll, Johnson gets 19 percent of voters younger than — but only 13 percent among voters 35-54 and 6 percent of voters 55 and older said they would vote for the former New Mexico governor.

In the CNN/ORC poll, Johnson and Stein take a combined 21 percent from respondents younger than 45, but just 8 percent among voters 45 and older.

Young voters don’t like Hillary but they loathe Trump, so they’ll vote for her — if they have to. If they have another option on the ballot, as they will this year, a chunk of those votes move to Johnson and Stein. If this race tightens eventually, Johnson may end up being Trump’s unwitting ace in the hole by keeping would-be Hillary voters out of her column. Then again, if the race tightens then anti-Trump young adults would essentially be in a situation where they have to vote for her or risk Trump winning the White House. Johnson and Stein may not be taking voters away from Hillary, in other words, so much as holding them for her in case she needs them. Some of them may come back to her to save the day, holding their noses all the way.

One last note before we leave McClatchy. It’s worth skimming the numbers on pages 7 and 8 here to see the contrast when Hillary’s voters and Trump’s voters are each asked whether they’re voting for their candidate or against the other party’s. Among those who say “for,” Clinton consistently polls in the 50s and 60s. Trump polls consistently in the 30s. It seems hard to believe that a candidate who’s already leading, and a majority of whose voters are enthusiastic-ish about her, is going to falter and lose to a candidate whose own base of support is notably less enthusiastic. But anything can happen in 2016, I guess.