The first and potentially only debate between Kamala Harris and Donald Trump is scheduled for Tuesday, September 10th at 9 PM eastern, at the National Constitution Center in Philadelphia. It could determine the White House.

Kamala Harris has established a lead over Donald Trump that seems durable nationally, but remains razor-thin in the crucial battleground state elections that are likely to determine the all-important Electoral Collage outcome.

The best public opinion analyzer in America isn’t a pollster, he’s a poll interpreter. Nate Silver doesn’t conduct polls, he crunches the data produced by the pollsters. But if you want the most accurate snapshot of where the race stands go to Nate Silver’s Silver Bulletin. The polls are always volatile, fickle and hard to predict, but if studied carefully can provide a wealth of insight as to where the race stands. There’s no one better than Nate Silver and he is quick to assert that he doesn’t have a crystal ball. But he does give you the best insight available.

As of Friday September 6h Nate Silver has Harris up by 3 points nationally, but by only an average of 0.6 points in the 6 battleground states that decided the last 2 presidential elections Pennsylvania, Michigan, Georgia, Wisconsin, Arizona and Nevada. That’s slender indeed.

Nate Silver also charts how far Harris will have to be ahead in national vote tallies to avoid Electoral Collage defeat. Bottom line, to steer safely clear of the Electoral Collage Kamala Harris needs to win the popular vote by at least 3.5 points. At 4 points or higher Harris looks secure at 3 points or lower odds favor Donald Trump in an Electoral Collage scenario.

The upcoming debate is crucial. It is possibly the last opportunity for either candidate have a substantial impact on public opinion. Harris does not need a great performance, but she needs to avoid anything damaging. She needs a strong steady showing.

Donald Trump gives Kamala Harris plenty of ammunition. He’s an easy target with tons of baggage. But Trump is also a deceptively adept tactician. In the 27 June debate with Joe Biden Trump handled the debate format more cleverly. When the moderators asked Biden a question Biden dutifully attempted to answer the question in a detailed and substantive way, it was commendable but ineffective as he became bogged down in policy details the public could not connect with.

Trump in contrast largely if not entirely ignored the moderator’s questions and used his time to attack Biden and repeat his talking points. Harris must not make the same mistake. Trump will not waste his time answering moderator questions. When his microphone is on he will be on the attack. Harris has to be prepared to fight fire with fire.

According to PBS 91% of Americans intend to watch the upcoming debate. It may well be the biggest political stage in US history. This race is at this point a bit too close for comfort. Harris needs a strong showing.