Donald Trump has to win Florida, North Carolina and Ohio.
He has to do a lot of other things, too: He has to hold Arizona and Texas and he has to win Iowa, for example.
He has to keep Utah's electoral votes in his pocket. But we'll give him all of those states, for the sake of argument.
To have a shot at the presidency, Trump needs to win Florida, North Carolina and Ohio - and if he does, and if the other must-wins above hold, he will pull to 259 electoral votes.
We've spent a lot of time talking about Florida recently because it has the most electoral votes of Trump's must-wins and because it has been the closest race of the three. If Trump loses Florida? Done. Over. President Hillary Clinton, once again. But if Trump wins Florida? It doesn't mean President Trump.
In RealClearPolitics' most recent polling averages in the state, Trump has a slight lead in Florida. Over the past two weeks, Hillary Clinton's once-decent-size lead in the state has collapsed. At the same time, Trump has grown stronger in Ohio and the national picture has tightened. But North Carolina hasn't really budged.
We're close enough now to Election Day that we need to point out that the RealClearPolitics polling average is a snapshot of the race as it was.
Things can and have changed before the polls pick them up, meaning that we're left with a sort of Heisenberg's uncertainty principle of polling: Our numbers necessarily reflect a race that no longer exists.
Clinton's lead in North Carolina is just about where it was right before the second debate. Her lead in Ohio at that point has since vanished; her lead in Florida lasted past the third debate. But in North Carolina, she has held steady.
This is important because holding North Carolina makes Trump's path to 270 electoral votes much, much harder.
If Clinton wins North Carolina, Trump's 259 electoral votes from the everything-goes-right scenario falls to 244 electoral votes. That means he probably needs to win at least three other states that aren't currently in his column to win the election.
He's unlikely to pick them up elsewhere in the Rust Belt. Despite his campaign's insistence that Pennsylvania or Michigan are in play - an insistence that seems in part to be a reason he keeps campaigning in the states - there's no evidence that he's narrowing Clinton's leads in either of those states or in Wisconsin.
Two recent polls from less-established pollsters have Trump within a few points in Pennsylvania, but a new poll from Franklin & Marshall College has Clinton up 11 points in a four-person race. (The poll also has the Democratic Senate candidate in the state up by double-digits, which seems unlikely.)
We hadn't seen many new polls in Michigan for a while, but a spate in the past week has Clinton up by six or seven points consistently. Last week, Trump's communications guy said that the campaign thought Michigan was in play; if it is, their polling shows a shift that no one else has captured. A poll showing Clinton up six points in the state was conducted after that claim was made.
So if Trump loses North Carolina and holds Arizona, he can get to 270 by winning Nevada and Pennsylvania. Nevada seems more possible: Clinton's lead in the poll average there is about two points. If he doesn't win Pennsylvania, he needs something like Colorado, Minnesota, Nevada and New Hampshire. That would get him to 273.
The Cook Political Report has three states as toss-ups now: Arizona, Florida and Ohio. (It also figures that one electoral vote in both Maine and Nebraska could be up for grabs.) Without any of those toss-ups, Clinton is at 293 electoral votes.
Dave Wasserman, an editor at Cook, figures that the easiest path for Trump to get to 270 is a meandering one, tweeting:
"Trump's path of least resistance to 270 increasingly looking like NC-FL-OH-IA-WI-ME02. https://t.co/PkHQBgZ0Fx"
This raises the point we made at the beginning: Even if Trump wins Florida, North Carolina and Ohio - his must-wins - he still needs to get 11 more electoral votes from somewhere.
If he doesn't win North Carolina (or Florida or Ohio)?