Good news for our many, many resident Christie-haters. He’s still going to win the election, almost certainly by double digits too, so his basic 2016 narrative as the guy who can conquer blue states that would vanquish other Republicans will remain intact. But Nate Cohn’s right: The more Democrats he loses on party lines to a weak unknown state opponent, the harder it’ll be for him to argue that national Democrats and independents will catch Christie fee-vah three years from now.

If you’re a Rand Paul fan who nonetheless wants Republican governors in control of the states, your magic number here is 51 percent.

The newest Monmouth University survey shows Christie holding a 20 point lead, 56 to 36, over Buono. That’s a 10 point decline from June, when Christie was up by 30 points, 61 to 31. It’s not surprising that the race is tightening: if you didn’t support Christie a few months ago, you were probably a Democratic-leaner who was going to end up with the Democrat. But the most significant part, as Enten observed, is that Christie’s support has actually declined by 5 points. Indeed, the poll shows that Christie’s support among Democrats has fallen from 36 percent to 21 percent. At the same time, Buono got closer to unifying New Jersey’s Democrats. She’s now at 71 percent, up from 59 percent in June. Christie’s support among independents has held firm…

According to just about every reported piece on the matter, the Christie camp wants to win by a massive margin. The type of margin that proves Christie can broaden the Republican coalition and force even the most reluctant conservatives to pay attention. But if Christie keeps bleeding Democrats, he might not get his wish. In 2009, 41 percent of voters were Democrats; just 31 percent were Republicans. If Buono continues to unify Democrats and manages a relatively unimpressive 85 percent of the Democratic vote, she’ll manage to get up into the low-to-mid forties—even if she still loses independents by a massive margin…

Would a 57-43 victory satisfy the Christie camp? What about 55-45? Hard to say. It would be impressive in my book: The best showing by a New Jersey Republican seeking the governorship, senate, or presidency in my lifetime. But it might be somewhat underwhelming or even disappointing in comparison to the gargantuan, 40 point lead he held early in the race, when he was still riding a post-Sandy, post-Obama bump.

His favorable rating in the new Monmouth Poll among indies is a robust 65/23. Among Democrats, it’s 32/61. Cohn’s writing for liberal TNR but if Christie sputters with Democratic voters in November — or, more significantly, starts to bleed independent votes — you’re way more likely to hear this point pushed next year by Republican critics, as a dagger to his “electability.” Yeah, yeah, they’ll say, it’s impressive to be reelected in a Democratic state, but who knows what might have happened if not for all the local residual goodwill he earned from the fluke of Sandy? People pull together behind the chief executive in the aftermath of a crisis; Bush’s approval rating zoomed to upwards of 90 percent after 9/11. Christie won’t have that sort of goodwill waiting for him nationally. Besides, he’s bound to start pandering to conservatives more after November to prepare for 2016 and the national Democratic press shop will make sure that their base hears about all of it. Right now Ted Cruz is liberal public enemy number one, but next year it’ll be Christie — especially if he wins by the gigantic margin his team is hoping for. They already have an election playbook for dogmatic righties like Paul and Cruz, but they’ll want to get started early tearing down someone more heterodox like the big guy.

Big question, then: What’s pulling Christie back to earth among Dems in New Jersey? Just political gravity at work, aided by Democratic attack ads? I’m tempted to say that his half-panders to the right on medical marijuana and gun rights have started to hurt him, but those were actually bigger panders to the left: He agreed to liberalize MM for kids subject to a few tweaks to the current bill and he signed several gun-control bills before carving out a symbolic exception for .50-caliber rifles. If that’s too “right-wing” for Jersey Dems, he’s playing to a tougher crowd than I thought.

Update: Touche.