And the convention comes in the middle of an extraordinarily violent period that has seen police shootings, huge protest marches, the Dallas police ambush, attacks in Orlando and Nice, France. More horrific news came with police officers killed in Baton Rouge.
"There's an awful lot of fear out there," said Jim Wilson, a retired law professor who participated in the bridge demonstration.
But even as local hospitals open up extra bed space in case of mass casualties, and battalions of police officers on bikes prepare to swarm around the protest areas, the city leaders here and many of the residents are determined to put a bright, sunny, Midwest Nice face on this week's GOP gathering.
"We are friendly. This is a good place to be. And we want people to come back," the mayor's media relations director, Daniel Williams, said.
There was no mistaking that a huge political wave was crashing upon this city. Many of the billboards have political messages, including one, from a group opposing homophobia, that features an artist's rendering of Trump about to engage in a lip lock with Senator Ted Cruz. An airplane circled the skies above Cleveland pulling a banner that said: "Hillary For Prison 2016". "Don't Trust the Liberal Media" an electronic billboard warned.
Jersey barriers, tall fencing and police checkpoints abound. There are multiple security zones. The delegates will assemble in the Quicken Loans Arena - known locally as "the Q" - while 15,000 media people will work nearby at the convention centre.
The city has said it expects 50,000 people. Although the Hope Memorial Bridge event was by far the largest demonstration of the day, the one that drew the most intense police presence began a few hours later, when several hundred protesters marched into downtown. Many were protesting against racism and calling for indictments of police who have shot unarmed African Americans.
The protest remained peaceful and everyone dispersed as the police slowly advanced, on horseback, bicycles and on foot.
The state has an open-carry law that permits people to walk around with loaded handguns or long guns.
"We're not going to impede their Second Amendment rights," Police Chief Calvin Williams said.
But he added that people have a legal responsibility not to menace anyone with those weapons - or be perceived as being menacing.
Of the convention Williams said: "I'm ready to get this started, to be honest. It's game time".
