So, what exactly is Milwaukee letting itself in for if it wins the right to host the 2020 Democratic National Convention?

Mike Grebe has some answers.

"It is an enormous undertaking," said Grebe, the former head of the Milwaukee-based Bradley Foundation who served on three GOP site selection committees and helped oversee his party's 1996 convention in San Diego.

Milwaukee, Houston and Miami are the three finalists to host the Democrats in 2020. A decision is due by the end of the month.

A convention isn't just four days of prime-time speeches. It's a near nonstop political festival of meetings, meals and media. An estimated 2,000 events occur outside the convention's main arena.

State delegations have their own schedule of events, speakers, meals and outings. Lobbyists and corporations sponsor special gatherings. In Milwaukee, that could mean a single state's delegation might have an early-morning cruise on the Milwaukee River followed by a union-sponsored lunch at the Milwaukee Art Museum, each featuring VIP guests to fire up the troops.

Multiply that by 50 states and numerous special interests, and you get the idea. All the moving parts need to be planned and coordinated, and it takes a lot of money to run.

You have to raise millions of dollars, secure rooms for thousands of delegates, journalists and visitors and set up a transportation system to ferry everyone through a city that is turned into a security zone.

The feds kick in around $50 million for security, with the U.S. Secret Service taking the lead and police from other agencies lending a hand to local law enforcement.

You need to recruit, train and deploy thousands of volunteers.

You even need to set up an area for protesters.

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Milwaukee has hosted large-scale events like Summerfest, Harley-Davidson birthday celebrations and the 2002 Major League Baseball All-Star Game.

But a convention, Grebe said, "will be bigger than any of those events you just mentioned."

"Law enforcement will be stressed," he said. "The city's transportation systems will be stressed. There will be lots of traffic in the downtown area, and if I'm correct in my assumption, they'll need to put people up in hotels in far-flung locations. There will be an enormous amount of bus traffic in and out of the downtown area."

But there are plenty of positives in hosting a convention, Grebe said.

"It will be great business for the hotels and restaurants," Grebe said. "I think it offers the city the opportunity to show itself off in the convention and meeting business and travel industry."

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One of the big hurdles for any local organizing committee is fundraising. The leaders putting together Milwaukee's bid have said they'll need to raise up to $70 million, with funds coming from local and national donors, corporations and unions.

The payoff: Organizers say the convention could bring $200 million in economic impact.

"Fundraising is a big lift and it's crucial," said Grebe, who recalled how fundraising issues cropped up for the local committee at the 1996 San Diego convention.

"We literally didn't know hours before the convention was to be gaveled in to start whether we were going to have power in the arena," he said. "The national chairman, Haley Barbour, pitched in and helped the city close the gap through fundraising efforts of his own. It's just crucial."

Lessons from Charlotte

The 2012 Democratic convention in Charlotte, North Carolina, serves as something of a cautionary tale. Because of a restriction on corporate donations, the local bid committee fell $10 million short of its fundraising goal and a line of credit had to be tapped.

Overall, though, Charlotte had a successful convention. The city has signed up for more. It will host the Republicans in 2020.

Cleveland, which hosted the GOP in 2016, probably provides the closest comparison to what a Milwaukee convention would be like.

David Gilbert, who was chief executive of Cleveland's 2016 local organizing committee, said: "If you really want to do more than just pull it off and maximize the benefit for the community, take the politics out of the community as it prepares."

That may sound strange. It is a political convention, after all. But Gilbert said it's important to "get 100 percent of the community behind" the event.

Asked if Cleveland was effectively shut down during the event, Gilbert said: "It all depends on how you define 'shut down.'

"There is certainly a tremendous amount of security, and ultimately the security apparatus will determine a security zone," he said.

Gilbert said public forums were held to tell local businesses and the public what to expect.

"It helped a huge amount in terms of businesses being able to operate easily," he said. "Think of little things like food deliveries. You have a lot of beer that is going to be served. and there is enhanced security around trucks coming in to deliver."

An extensive transportation system was set up, with buses brought in from around the country.

Thousands of volunteers were used, both inside the convention hall and outside. The local ambassadors greeted delegates at the airport and were also stationed at hotels and on busy streets.

A lot of spending took place at private events that were spread across the city, from restaurants and banquet spaces to converted warehouses and parking lots outfitted with fancy tents. Conventions are something of a foodfest, with a lot of people looking for free meals.

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Gilbert can't stress enough the importance of fundraising.

"We had to fundraise during and after the convention," he said.

Ultimately, Cleveland exceeded its target, raising $65.7 million in cash and in-kind contributions.

"It is still something our community is incredibly proud we hosted and hosted well," Gilbert said. "For a city like Cleveland, a city like Milwaukee, it is not just hosting another convention. It is something more grand and meaningful."