It all comes down to Pennsylvania.

That is not an exaggeration.

If Kamala Harris loses Pennsylvania, Donald Trump is the 47th president of the United States.

Now you could say the same about Michigan or Wisconsin, but it especially seems that a Democratic candidate should be able to carry the Keystone State.

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And that’s why, in my view, Kamala should have picked Josh Shapiro, its popular governor.

I have nothing against Tim Walz, of football coach fame, but I don’t see what he’s done for the ticket. There’s a reason the campaign hasn’t let him do any solo interviews – a stark contrast with JD Vance, who is constantly doing interviews and holding press conferences.

In fact, Vance now frequently takes reporters’ questions in front of supporters, who boo the journalists, sometimes even before they start speaking.

We’ll find out whether Walz can think on his feet when he faces off against Vance in tonight’s VP debate. The most generous thing I can say is that the Coach will be rusty.

Let’s look at the latest numbers.

The Real Clear Politics average has Trump leading Harris by a miniscule margin, 48.1% to 47.9%, which of course is a statistical tie.

At 538, the micro-margin in Pennsylvania is flipped, with Harris averaging 47.9% and Trump at 47.1%, another tie.

Now imagine that Shapiro, who is more of a moderate liberal than the uber-progressive Walz, was the running mate. And let’s say Shapiro had brought in another 50,000 votes as the home-state guy. You can see where that would tip the balance.

Kamala didn’t pick Josh for two reasons. They had a rough conversation when she interviewed him, with the governor insisting on an influential role if he were to relinquish his current job. But so what? Presidents and their veeps often don’t see eye to eye. She preferred the image of Walz, hunter and fisherman, to the prospect of two East Coast lawyers.

But the more important reason is more troubling. Harris was under pressure from the anti-Israel faction in her party not to tap Shapiro, who is Jewish and a strong supporter of the Jewish state.

So the vice president effectively handed veto power to this minority faction, which basically backs the Hamas terrorists who would wipe out Israel, and would have faced a week or two of controversy as a result. I said at the time this would be a world-class mistake if she lost Pennsylvania.

The reason Harris has spent so much time in the Pittsburgh area is that the western end of the state is much more conservative than the eastern section anchored by Philadelphia. Her goal is to hold down Trump’s margin in a part of the state that he’ll easily win.

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One problem Harris faces right now is that she makes little news. By picking "friendly" interviewers, such as MSNBC’s Stephanie Ruhle, who has trashed Trump as a danger to democracy, she avoids tough questions and followups. 

Visiting the Mexican border was a smart move, not just because Trump has a major lead on immigration, but because Harris broke into the news cycle, where images can count more than words, and attempted to position herself as tougher than Joe Biden on the issue.

Otherwise, I’m just hearing chunks of her stump speech in response to questions, starting with how her mother raised her. Repetition is important in politics, but if you don’t throw in a few new lines, the press is left without a headline.

Meanwhile, Trump over the weekend called Harris "mentally impaired," saying Biden just got old but she was born that way. He also said Harris should be impeached, and maybe prosecuted, for the way she helped run the country.

Now that is classic Trump. By using over-the-top rhetoric, he sparks a media debate about whether he’s gone too far, and that debate revolves around the words "Kamala" and "mentally impaired." 

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Harris has wisely not responded to every Trump jab. But remember, Trump benefits from negative coverage as much as positive coverage because he’s driving the news agenda.

Here’s a pool report from Harris at a West Coast political event over the weekend: "She then switched her remarks to talking about the need for comprehensive immigration reform. VP Harris remarks on the issue were very similar to her remarks in Arizona on Friday." In other words, no news.

Think about this: Trump has been absolutely pummeled by a hostile press corps, is a twice-impeached convicted felon and carries the burden of Jan. 6. Harris has been riding an extraordinary wave of positive press, and yet she’s slipped slightly in the polls and is tied in Pennsylvania.

And there’s no question that if she loses there, the election is over.