LOS ANGELES >> Los Angeles’ roller-coaster campaign to host the Olympics — an effort marked by early defeat and last-second negotiations — reached its conclusion today when the city was formally awarded the 2028 Summer Games.

International Olympic Committee members, by a unanimous show of hands, voted their approval at a session in Lima, Peru, ending an unusual bid competition that resulted in two winners as Paris was simultaneously given the 2024 Games.

“Everyone connected with LA 2028 is thrilled to be part of this win-win-win scenario for the Olympic movement,” bid leader Casey Wasserman said in a statement. “Together, L.A., Paris and the IOC will demonstrate the Games’ enduring value to host communities.”

Immediately after the vote, Mayor Eric Garcetti signed the controversial “host city contract,” promising the city government will serve as a financial backstop, paying off any debts should the estimated $5.3 billion sporting event run over budget.

LA 2028 has sought to cut costs by using existing venues such as the Coliseum and Staples Center. Bid leaders estimate they can cover all expenses through revenues from broadcast rights, sponsorships, ticket sales and other sources.

“This is the moment Angelenos have been waiting for,” Garcetti said.

But critics have noted that a slew of previous hosts — including Rio de Janeiro, which staged the 2016 Summer Games — have ended up with substantial deficits.

“Despite the fact that the IOC has awarded L.A. the bid to host the 2028 Summer Olympics, the fight isn’t over,” the NOlympics LA group said in a statement. “The notion that ‘L.A. is going to have the Olympics, one way or another’ isn’t necessarily true, as many opportunities still exist to intervene and stop them entirely.”

Today’s vote took place during a tumultuous session for the IOC, which is facing separate bid scandals involving 2016 Rio de Janeiro and 2020 Tokyo.

“The IOC Ethics Commission is following up on this matter,” the committee announced in a statement this week. “Where evidence is provided, we will act.”

Neither L.A. nor Paris has been implicated in any wrongdoing, so the host-city selection proceeded smoothly with the candidates giving brief presentations before the ratifying vote.

L.A.’s fait accompli presentation lasted 30 minutes with three videos and a series of eight speakers thanked each other, thanked the Olympic movement, thanked Paris and portrayed the self-congratulatory tone that has become the hallmark of some IOC meetings.

The delegation came to the stage wearing sneakers, which Wasserman talked about in his speech.

“Now, I know what you’re thinking … these LA guys seem pretty laid back,” Wasserman said. ” … My grandfather told me the key to success was two simple things: Always be honest, and always stay true to who you are. Well, what you see onstage here today reflects who we are, and the unique brand of California-cool that we will bring to the 2028 Games.”

Larry Probst, U.S. Olympic Committee chairman of the board, came the closest to any negative tone when he said: “It has been a formidable journey to get here, but we never gave up hope or confidence in our ability to support and advance the Olympic Movement.”

It was two years ago that L.A.’s effort appeared to be over after the city lost to Boston in a competition to become the sole American bidder.

But when the Massachusetts capital withdrew over cost concerns, L.A. quickly stepped into what eventually became a two-city race with Paris for the 2024 Games.

The competition, which appeared to be close, took a dramatic turn with talk of the IOC naming two winners, giving 2024 to one city and 2028 to the other.

The move made sense because there have been so few candidate cities, so with two viable bids, Olympic leaders warmed to the idea of locking up summer hosts for the next 11 years.

The only question was: Which city would agree to take 2028?

From the start, Paris insisted it could not wait around. Negotiations between L.A. and the IOC began in earnest last July and, by early August, the deal was done.

In return for going second, L.A. will not have to pay tens of millions in IOC fees and will receive a $180 million advance, most of which will go to funding youth programs citywide beginning as soon as next year.

The rechristened LA 2028 committee will also get a larger slice of IOC revenues and will not have to give the IOC a standard 20 percent of its surplus if the Games run under budget.

The Los Angeles City Council unanimously supported the agreement at a session marked by vocal protests last month.

“Today, LA 2028 is taking the final step in our bid, and preparing to begin our 11-year journey as an Olympic host city,” Garcetti said. “I am thrilled to begin the next chapter of this process.”