Sunday, the reelection campaign that President Donald Trump officially opened on the day he was inaugurated enters the final stretch. Democratic challenger Joe Biden holds a lead nationwide of 8.6 percentage points, 49.3%-40.7%, according to the RealClearPolitics.com average of recent surveys. That advantage is steady enough that some politicians in both parties have begun calculating what to do in a post-Trump era.

What could shake things up?

Possibilities include the development of a safe and effective vaccine against COVID-19, an optimistic turn in the pandemic that has redefined the campaign. An economic rebound or new downturn. A presidential debate that either raises questions about Biden’s acuity – a caustic theme of Trump’s campaign – or reinforces dissatisfaction with Trump’s leadership.

History says it’s premature to assume that the campaign is settled. In three of the past 10 elections, the candidate with at least a narrow lead at the end of July lost the popular vote in November, although two of them carried the Electoral College and won the White House anyway. In another three elections, the candidate with no more than a narrow lead in late July won in a blowout.

That said, since 1980, only one candidate was clearly ahead at this point, then lost the election. That was Democrat Michael Dukakis in 1988.