THE MORNING PLUM:

The new Washington Post/ABC News national tracking poll finds Donald Trump leading Clinton by one point in the four-way match-up, 46-45, while Clinton leads in the head-to-head by 48-47. You shouldn’t overreact to individual polls — instead, keep focused on the national and state polling averages.

But plainly, the race is tightening, and it’s increasingly possible we’ll see a very close finish. Which means that it’s time to start pondering an Election Day nightmare scenario that is made up of two parts. First, the tight finish produces an outcome that is contested well beyond Election Day, with Trump (should he lose) claiming the results are rigged. Second, Trump supplements his claim about the rigged outcome by continuing to point to the FBI’s latest discovery of emails as proof of an ongoing cover-up of Hillary Clinton’s criminality.

This morning, election rules expert Michael McDonald argues in USA Today that if the outcome is close, the election could very well “go into overtime,” adding that “in this environment,” this could “rip this country apart.” McDonald posits that in a very close finish, Trump could be favored on election night, but over subsequent days, as the vote counting continues afterwards, Clinton might then edge into the lead:

A Democratic shift from election night to the final tally of votes is predictable. All states count some ballots late, and those tend to break towards Democrats. Nothing nefarious occurs: the casting and counting follow procedures laid out in state law. Some of the states that count more late ballots are key battlegrounds, magnifying the suspense on Election Night.

Mail ballots are one of two types that can shift election results. Many states require mail ballots to be received by election officials on Election Day. Others continue to accept ballots postmarked on Election Day, up to two weeks following the election. Among these states are Iowa, North Carolina, Ohio, and Wisconsin.

These late ballots may break towards the Democrats. My analysis shows more Democrats than Republicans in Iowa and North Carolina have yet to return their mail ballots. Why? These voters tend to be younger people who tend to return their ballots later. If Trump is slightly ahead in a late mail-ballot return state, he could fall behind after all the mail ballots are counted.

Then there are provisional ballots. States are required under federal law to provide them to anyone with a problem at the polls — a voter who doesn’t have the required form of ID, for instance, or whose name is missing from the voter registration rolls. Election officials review provisional ballots and allow voters to clarify their eligibility after Election Day. In the four states that report separate results for provisional ballots, the voters who cast them broke strongly for the Democrats. So if the presidential race is particularly close, provisional ballots could tilt it.

There’s still more in the link, but you get the idea. Meanwhile, Bloomberg Politics reports that both sides are now gearing up in a serious way for the possibility of a legally contested outcome.

With one week to go, Donald Trump and Hillary Clinton are in a statistical dead heat nationally. The Fix's Chris Cillizza explains what you should expect from the last week of the election. (Peter Stevenson/The Washington Post)

All of that is worrying enough, because as you’ll recall, Trump has refused to say that he’ll accept the outcome if he loses. Even when he clarified this, he explicitly left open the possibility that he would legally contest the outcome if the result is “questionable,” reserving, of course, the right to define what counts as “questionable” for himself. It’s Trump’s right to contest a close, legally murky loss. But, given his continuing insistence that the election is “rigged,” it’s plausible he may go a lot further, and launch a sustained campaign well outside of conventional channels to cast Clinton as an illegitimate president, no matter what our political norms and the electoral and legal realities actually dictate.

What’s more, you cannot mull this possibility without also connecting it to the ongoing battle over the new emails discovered by the FBI. As I’ve noted, Trump is now explicitly arguing to his followers that FBI director James Comey has two choices — either he discovers new evidence of Clinton’s criminality in the discovered emails, or Trump will revert to casting Comey as a participant in a cover-up of that criminality that is designed to deliver the election to Clinton.

And there is no obvious way for Comey to resolve this problem. Or, at least, there is no obvious way to resolve it — short of turning up something new and incriminating in the emails, which can’t be ruled out — that would avert an outcome that Trump casts as corrupt and illegitimate. If Comey announces before the election that he has found no new grounds to revisit his July decision not to recommend charges against Clinton — and if Trump loses — Trump will claim that Comey’s finding was rigged to help elect her president. If Comey does not announce any new finding from the emails — and if Trump loses — Trump will claim that Comey’s failure to produce anything in time was rigged to help elect her president. And then, if and when Comey does eventually clear her, that, too, will constitute still more evidence that the system is rigged, and thus more grounds for grievance.

Many Republican voters will accept whichever of these explanations is relevant. See how this works?

Add to all of this the fact that Trump and his campaign CEO Stephen Bannon are reportedly looking to convert the campaign into a vehicle for sustaining a post-election following. All of these narratives could then converge and become the fuel to drive that vehicle forward. And so, it’s not hard to see a close finish producing an aftermath that gets very ugly and destructive. Which is exactly what Trump would relish.

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* INTERNAL POLLING SHOWS LITTLE SHIFT: The New York Times reports these nuggets about the overall map and about North Carolina:

The F.B.I. director’s letter about the emails has not yet produced a major shift in private polling, according to Republican and Democratic strategists….Mrs. Clinton’s lead over Mr. Trump appears to have contracted modestly, but not enough to threaten her advantage over all…Republicans privy to private polling data said surveys they had seen since the news from the F.B.I. on Friday still showed Mrs. Clinton leading in North Carolina.

Trump must win North Carolina. As the Times notes, Trump is campaigning Michigan and New Mexico, meaning he knows traditional routes to victory are closed off and hopes for a miracle.

* FBI SIFTING THROUGH NEW EMAILS: The Post reports that the FBI is right now examining the newly discovered emails with software that can identify whether they are duplicates or contain classified information:

It should not take long for the FBI to determine if there are emails that are duplicates of ones already collected in the probe, bureau experts said. But if the bureau finds emails that contain potentially classified information, getting those analyzed could take weeks because the agencies whose information was being discussed would need to review them, officials said.

So it’s at least possible that this could be settled before the election, if they are found to be duplicates. But it’s still unclear whether the FBI will say anything more before the voting.

* TRUMP’S TAX AVOIDANCE MANEUVER IS VERY SMART: The New York Times turns up new evidence that Trump may have avoided paying hundreds of millions of dollars in taxes by stretching a loophole to what experts call an extraordinary degree. Note this:

Moreover, the tax experts said the maneuver trampled a core tenet of American tax policy by conferring enormous tax benefits on Mr. Trump for losing vast amounts of other people’s money — in this case, money investors and banks had entrusted to him to build a casino empire in Atlantic City.

No doubt Trump would say that this, too, “makes me smart.”

* CLINTON LEADING BIG IN PENNSYLVANIA? A new Franklin and Marshall College poll finds Clinton leading Trump by 49-38 among likely voters in Pennsylvania. Still, be cautious: this poll also finds Dem Katie McGinty leading GOP Senator Pat Toomey by 12 points, suggesting it could be an outlier.

Also: 80 percent of the interviews were completed before the FBI news broke. The polling averages put her up six points, but we need more post-FBI data. If her lead holds here, that will be a big tell.

* BURST OF DEM SPENDING SUGGESTS TIGHTENING RACE: The pro-Clinton Super PAC Priorities USA is set to unleash millions more in ad spending, and note where that money is going:

Some of the spending will occur in Wisconsin, a state where the group had not previously spent any money this election and where Donald J. Trump is running close to Mrs. Clinton. Priorities USA Action will also spend money in Miami and Jacksonville, Fla., for the first time, while adding to its spending across cities in Pennsylvania.

This suggests internal Dem data shows a real tightening in Wisconsin and Pennsylvania, two states that should be safe for Clinton but that Trump really might be making competitive.

* AFRICAN AMERICAN TURNOUT LAGS IN FLORIDA: Politico’s Marc Caputo reports that Democrats are worried about the weak early voting turnout they are seeing among African Americans in Florida:

After Sunday night’s polls closed, black voters accounted for 16 percent of the in-person early vote ballots cast. And that included five previous days of in-person early voting. But in 2012, in just two days of in-person early voting, blacks cast 25 percent of those early ballots…Due to such strong African-American turnout after the beginning of in-person early voting in 2012, Democrats began outpacing Republicans in total ballots cast before Election Day, by about 10,000. This year, though, Republicans still cling to their own lead of about 9,000.

The Republican lead in overall early voting in Florida is razor thin, so there’s still time for Democrats to take the lead, but Florida is likely to be super-close, so this lag among African Americans could matter.

* FBI NEWS COULD SWING BATTLE FOR SENATE: FiveThirtyEight’s Harry Enten notes that five Senate races (Missouri, Nevada, New Hampshire, Pennsylvania, and North Carolina) are within two points, and explains why the emails might shift them:

All these races are so close that a small shift…could swing things. A 2-percentage-point lead just isn’t that safe…we’ve seen that when Clinton’s numbers have gone done this year, so too have Democratic Senate candidates’….there’s been an increasingly strong relationship between Senate and presidential election results….it’s not difficult to imagine that the latest news might push a few more voters to want a Republican Congress as a check on Clinton.

Even if the new emails turn out to be nothing whatsoever, James Comey’s mere release of the letter could help determine which party controls the Senate, with untold consequences. Nice!

* AND THE TRUMP RALLY MOMENT OF THE DAY, LOCK-HER-UP EDITION: Lovely:

In Michigan when Trump first brought up Clinton’s emails, the crowd began to loudly chant: “Lock her up! Lock her up!” In the audience was a woman dressed up in an orange prison jumpsuit labeled “Clinton.”

Imagine how Trump voters will react if Comey announces that the emails contain zero cause to revisit the decision not to recommend criminal charges.