Supporters of bringing the Republican National Convention to Charlotte tout what they believe will be a major economic impact for the city, but a Defenders investigation found host cities often over-promise and then under-deliver.

"The word of caution is that everybody's not going to get rich out of this," UNC Charlotte Political Science Professor Eric Heberlig said. "It's not like there's money going to be reigning down on everybody and making a huge difference on the city economy."

Before the 2012 Democratic National Convention in the Queen City, some suggested there'd be an economic impact of up to $250 million. Instead, the final number came in well below that at roughly $164 million.

Heberlig said there's no doubt the hotels, taxis and caterers will see a boost, but not the overall economy. He supported bringing the convention here for another reason.

"It's really about marketing the city, helping our reputation," he said.

Heberlig said economic impact projections are often inflated in an effort to get people on board. Research supports that.

"Chamber of commerce types have an incentive to inflate these," he said. "The hospitality industry has an incentive to inflate the economic impact."

At the 2016 DNC in Philadelphia, for example, the final economic impact number came in at about $230 million, which is not bad until you consider the original projection of $350 million.

The RNC in Cleveland that same year resulted in a $142 to $188 million economic impact depending on which study you read. It may sound good, but those numbers fell well below the projection of $200 million.

In Charlotte four years prior, businesses close to the DNC felt a positive bump thanks to the $164 million economic impact, but others walked away disappointed.

The Charlotte Regional Visitors Authority is playing it safe with its projections.

"We don't project future economic impact because you really want to have all the facts before you get it," CEO Tom Murray said.

That said, Murray hoped the 2020 RNC at least matches the city's historic number from 2012.

"That was a big impact for our community. In fact, it's historically the largest economic impact we've ever had," he said. "We expect that to be in that range if not bigger."

The $164 million economic impact from the 2012 DNC in Charlotte is lower than just about every other convention in recent years, but Heberlig believes that's because Charlotte measured the impact accurately.