With the focus once again on what e-mails might or might not be found implicating Hillary Clinton in misdeeds, the polls are narrowing. Nationally, Donald Trump is behind by only two percentage points, according to the RealClearPolitics compendium of polls. Mr. Trump could become president.

But before you reach for the bottle, take another look at the electoral map. Most evidence suggests that the Blue Wall remains intact. Ms. Clinton is still heavily favoured to prevail.

Remember, to become president, a candidate must win 270 votes in the electoral college. Each state is assigned a certain number of votes, based on its population. Win the popular vote in the state and (with a couple of minor exceptions) you win that state's electoral college votes.

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The Democrats go into any election with a huge advantage. They can reliably count on big states such as California (55 electoral college votes) and New York (29 votes). Among big states, the Republicans can count only on Texas (38).

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This means that, even before the battleground states are factored in, any Democratic candidate can count on something like 242 electoral college votes – states that have voted Democrat in each of the past six elections. This is the Blue Wall. Mr. Trump, with one exception, has failed to put any of these states back into play.

Now to the battlegrounds. Florida, with 29 electoral college votes, is too close to call. So are Ohio (18), North Carolina (15), Arizona (11) Iowa (6) and Nevada (6). Let's assume Mr. Trump has a very good night on Nov. 8. Let's give him every one of these battlegrounds, along with his base of solidly Republican states. That would probably give Mr. Trump 264 electoral college votes, only six votes shy of victory. And here is where he hits the wall.

Pennsylvania, the Keystone State, truly is key to this election, with 20 electoral college votes. Though historically part of the Blue Wall, Mr. Trump has been working hard to flip it.

Then there is Virginia, with 13 votes. The affluent suburbs outside the District of Columbia, plus a growing Latino population, have pushed Virginia into the Democrats' column in recent elections.

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The RealClearPolitics average has Ms. Clinton up by six percentage points in Pennsylvania and five in Virginia. That's probably too big a gap for Mr. Trump to close.

Does Mr. Trump have any path to victory other than through Pennsylvania or Virginia? Yes, but it's a tortuous path.

In Wisconsin (10 electoral college votes), Ms. Clinton currently leads by six points; in Colorado (9), she is up by four. (New Mexico and New Hampshire, with five votes each, aren't big enough to put him over, and Ms. Clinton leads in both states, anyway.)

To win, then, Mr. Trump must take Florida, Ohio, North Carolina, Iowa, Arizona, Nevada and one of Pennsylvania, Virginia, Wisconsin or Colorado.

Possible? Yes. Probable? No.

There is also the question of organization. The Democrats have raised far more money than the Republicans, and have a far more sophisticated get-out-the-vote operation in the battleground states.

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It is far more likely that, on election night, Ms. Clinton will do better than the polls suggest, rather than worse, thanks to her powerful machine.

To flood and stall that engine, Mr. Trump will have to count on a wave of enthusiastic supporters. But let's not forget: He remains even more unpopular than she is.

Then there is the advance vote. Some states offer previews of the types of voters who have already cast ballots, such as how many registered Republicans or Democrats voted, and the racial mix of the advance electorate. Early indications are encouraging for Democrats in Nevada, North Carolina, Colorado and even Iowa.

This election has done nothing but surprise. More surprises could yet be in store. But however jittery Democratic supporters may be right now, the electoral evidence still strongly favours a president Clinton.

If Donald Trump wins this election, he'll have earned it.