Dennis DeWitt says he typically doesn’t get involved in politics until it is time to vote, but he took the opportunity here Friday to throw his support behind President Trump in the Iowa State Fair’s popular “corn kernel poll.”

Mr. Trump is showing his strength in the informal survey of fairgoers, which through Thursday night showed that half of the more than 4,700 kernels cast had gone for Republicans and half had gone for Democrats.

It’s just a few days on the political calendar, but what happens at the Iowa State Fair can echo through an entire presidential race.

It takes on its political significance in the year before a presidential election (that’s now). Because most presidential campaigns circle this event in red on their calendars, Washington Post reporters have covered the Iowa State Fair for years. Below is some of what they, and The Fix, have learned about it.

DES MOINES, Iowa (AP) — Former Vice President Joe Biden and Montana Gov. Steve Bullock opened the Iowa State Fair’s 2020 presidential blitz on Thursday by blistering President Donald Trump and promising to push new gun restrictions.

“I believe everything the president’s said and done encourages white supremacists,” Biden said as Trump continued to take criticism for his handling of back-to-back mass shootings. One of the shooters is believed to have written a racist screed echoing some of Trump’s incendiary language about immigrants.