As pretty much everyone expected, the polls have tightened in the race for the White House. Gone is the seemingly insurmountable eight-point lead Democratic presidential nominee Hillary Clinton boasted six weeks ago following the Democratic National Convention.

The momentum appears to be on GOP presidential nominee Donald Trump’s side, for now. Meanwhile, Clinton’s struggles with questions about her family’s charitable foundation and use of an unauthorized email server were compounded earlier this month when she referred to Trump supporters as “deplorables” and was caught on video collapsing while leaving the 9/11 memorial service in New York City.

Since polls are a lagging indicator of the race, Trump could still very well move ahead in the coming week. But don’t get too excited if you’re a Trump supporter.

The prediction markets still see the Republican candidate as a 2-to-1 underdog, even as the polls tighten a month and a half before Election Day. As we get closer, there will be some moments to watch for that could turn the contest on its head.

The presidential debates: With the first debate set to take place at Hofstra University in Hempstead, New York, next week, Trump has managed to get within striking distance of Clinton, which is where he needs to be. This will be the first Americans will see the two candidates in action. There will be two more after that — Washington University in St. Louis, Missouri, and at the University of Nevada in Las Vegas, in addition to the vice presidential debate at Longwood University in Farmville, Virginia.

In some election years, the debates have no effect on the race and in others they completely swing the race.

The first presidential debate will probably set viewership records, given Trump’s track record in this format throughout the primary. The polls after the debates will really be the ones to watch. The debates following might not draw as big an audience, so that first impression will be vital to each of the candidates’ path to victory on election night.

The October surprise(s): It’s long been a part of electioneering in presidential races. A campaign will have something negative on its opponent that it keeps quiet until late in the contest that could sway the race just enough.

These close races are decided by a handful of percentage points in battleground states, so if a campaign releases something shocking while the media are in presidential campaign overdrive, it is very effective.

Some examples in our recent election history include revelations about George W. Bush’s drunk driving arrest in Maine in 1976 during the 2000 presidential election and the Mark Foley scandal, which involved a Florida Republican congressman’s ouster following revelations he exchanged inappropriate messages with underage congressional pages.

As Election Day approaches, this cycle’s October surprise could come in the form of Trump’s past business dealings or more hacked emails of Clinton’s in the form of a release from WikiLeaks’ Julian Assange.

A terror attack: After last weekend’s bombings in New York City and New Jersey and the stabbing attack at a mall in Minnesota by a man of Somali descent, another terror attack before the election seems to be almost a certainty.

Fear in the electorate is something the candidates will have to grapple with, which could wind up being an advantage depending on how well they adapt if such an unfortunate event takes place.

George W. Bush was able to successfully lead his party to victories in the 2002 midterm elections and in his own re-election effort in 2004 after the Sept. 11, 2001, terror attacks.

Election Day weather: This a bigger deal than people realize. If it’s raining and cold, the candidate whose supporters are the most likely to brave the elements and go stand in line outside, potentially for hours, to cast a ballot could decide the election.

This variable will likely come into play more in the swing states where both of the campaigns are hustling to get out the vote. If it is a rainy day in Columbus, Ohio, it will become a question of voter enthusiasm, which is who has the most dedicated voters to go out and participate in the election.

Four or five days out, watch the weather forecasts in the close battleground states and in particular the more Democrat- and Republican-leaning part of those states.

The unknowns — Hillary’s health/Trump’s taxes: These appear to be the two biggest unknowns for a lot of people.

Americans saw Hillary stumble once. We were all told it was walking pneumonia and that it was no big deal.

OK, fair enough. But if she does take another tumble, it could kill her campaign. Her honest and trustworthy numbers are already low. If it is shown she lied to Americans about her health because she had another episode, that could be the death knell.

As for Trump, his Achilles heel could very well be what is in his tax returns. His honest and trustworthy numbers aren’t setting the world on fire, either. This will certainly continue to be a cloud hanging over the campaign.

What could be in these tax returns? Shady business deals? Him exaggerating his income? It would appear to be a no-win situation for him to release them because almost certainly the media will find something wrong.

But if Trump’s tax returns are released, it could swing the election for Hillary.