Republican presidential front-runner Donald Trump is bringing his campaign to California and has picked the OC Fair & Event Center in Costa Mesa for a kickoff rally Thursday night.

The 7 p.m. event comes as Trump gears up for California’s June 7 primary, which could determine whether he reaches the 1,237 delegates needed to secure the GOP nomination in advance of the Republican National Convention in July.

Both backers and foes of the polarizing billionaire are expected at the 8,200-seat Pacific Amphitheatre, where the rally will take place.

“I’ve never gotten this involved in politics before, but I think we need to shake up the whole system, and that’s what Trump is going to do,” said Mission Viejo’s Werner Raes, a retired police officer who reserved tickets for himself and his wife on Trump’s campaign website.

“I’ve never been to a rally, but I want to do everything I can to support him,” he said. “When the cameras roll, I want them to show thousands of people.”

Sen. Ted Cruz, R-Texas – Trump’s closest contender – has been laying the groundwork for his California campaign for more than eight months. By contrast, Trump has just begun gearing up his effort here.

The O.C. rally is part of a California swing that includes a luncheon speech Friday at the state GOP convention in Burlingame.

It was roughly two weeks ago that Trump hired veteran California GOP strategist Tim Clark to lead his state campaign. About the same time, he confirmed his attendance at the state Republican Party gathering, the last of the three remaining Republican presidential candidates to do so.

Aliso Viejo’s Mary Young said she was named last week as Orange and Los Angeles County co-chairman for the Trump campaign and is rounding up volunteers and preparing to open an Orange County campaign office.

A pro-Trump super PAC, Great America PAC, advised donors Monday that it would conduct polls in the state’s 53 congressional districts to determine where to focus efforts most effectively.

In California, Republican presidential candidates are awarded three delegates for each congressional district they win.

Wednesday’s announcement of the Trump rally came a day after the Anaheim City Council declined to approve, on a 3-2 vote, a proposed resolution condemning Trump’s “divisive rhetoric” in the presidential race. The council meeting was preceded by a clash outside between an estimated 50 pro- and anti-Trump demonstrators.

Five people were pepper-sprayed during an altercation among members of the crowd. Three were treated at the scene and two didn’t require treatment, Anaheim police Sgt. Daron Wyatt said. Police were working to find the sprayer, he said.

The Democratic Party of Orange County and Orange County Young Democrats are planning a demonstration at the Thursday event, writing on Facebook, “We in Orange County do not agree with his bigoted and misogynistic ways and we will not stand quietly as he brings these views into our county!”

The party asked that attendees protest peacefully.

Anti-Trump Republicans have raised the possibility of nominating someone else at the convention, if Trump has the most delegates but fails to reach the required 1,237 majority. If he falls short of that threshold, it would allow voting to proceed past the first ballot and delegates no longer would be obliged to back their original candidate.

That possibility has increased the urgency for the Trump campaign to reach the majority ahead of the convention. California’s 172 delegates – the most of any state – are a key prize.

County GOP Chairman Fred Whitaker said the party here was not involved in planning today’s rally.

“Unlike other campaigns, they haven’t called us to ask for assistance,” Whitaker said. “They run things their own way. They have their own event planners.”

Asked if he was proud to have Trump appearing in his county, Whitaker said, “It’s significant that he chose Orange County.” He said he’ll be traveling to Burlingame this evening for the GOP convention and will be unable to attend the Trump rally.

Reservations are required to attend the event and can be made on Trump’s website, donaldjtrump.com. Doors are scheduled to open at 4 p.m.

Orange County Sheriff’s Department Capt. Jeff Hallock said the department is preparing to deploy more than 20 deputies in and around the venue.

“We’ll have another group of deputies prepared to respond on immediate request,” he said. The additional deputies will be fulfilling their normal day-to-day duties unless an emergency situation arises at the fairgrounds.

“We can double our numbers in a matter of minutes,” Hallock said.

Staff writers Chris Haire and Alyssa Duranty contributed to this story.