The Iowa diner known as Hamburg Inn No. 2 first made its way onto the national political map when Ronald Reagan, one of the most popular presidents of his era, stopped there on a post-White House speaking jaunt.

Ten years later, the eatery hosted another president, Bill Clinton.

In a state long known for its influential spot on the presidential nomination calendar, that was enough to start a tradition, not to mention word-of-mouth marketing that attracted all manner of political hopefuls.

"Shortly after was when we started Coffee Bean Caucus, and that’s when it really picked up,” Seth Dudley, general manager of the Hamburg Inn, told FOX Business.

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The Coffee Bean Caucus is a straw poll where diners place a coffee bean into a mason jar that represents their preferred candidate. The caucus first gained attention on the local news, then got picked up nationally and before long was featured in an episode of "The West Wing."

More recently, then-Sen. Barack Obama of Illinois visited during his successful bid for the White House, as did a number of hopefuls including former Republican Govs. Mike Huckabee of Arkansas and Chris Christie of New Jersey.

Due to the Hamburg Inn's location in Johnson County, a Democratic stronghold in the eastern part of the state that is home to the University of Iowa, the voting skews liberal.

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The area's left-leaning nature is evident just from looking at the results of the 2020 Democratic Primary Coffee Bean Caucus, which showed Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren as the top two choices with 1,188 and 779 coffee beans, respectively. Biden polled fifth, with 223 beans.

Although the bean count is a sliver of the norm due to customers being limited to takeout and patio dining, voters in the area appear to have coalesced around Biden, much like they did former Secretary of State Hillary Clinton in 2016. A final tally is expected just before the Nov. 3 election.

Trump, meanwhile, during the 2020 primary received 493 beans, or 91%, that were cast for a Republican candidate. Back in 2016, he became the first Republican since Reagan to carry more than 50% of the Iowa vote.

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The Coffee Bean Caucus is “not necessarily a good indicator of how the whole state will go, but it's a good indicator of how Iowa City, Johnson County, and sometimes even eastern Iowa will go,” Dudley said.