They didn’t qualify for the debate stage. Now, they’re vowing to take legal action.

Holding his own press conference outside the debate venue earlier Wednesday, Elder said he would file a formal complaint with the Federal Election Commission if wasn’t allowed on stage -- which he later followed through on.

ABC asked him if he still plans on watching or attending the debate if they don't respond, to which he said: "I'll be there, one way or the other, but I'm going to be up on that stage, trust me. If I were a betting person, and I'm not, I would bet the forum that Larry Elder is going to be on that debate stage.”

Johnson is planning to file two lawsuits against the GOP, he said in an interview with ABC News Radio National Correspondent Steven Portnoy.

Ahead of the debate, Johnson’s team was spotted across the street from the Fiserv Forum wearing "Perry vs Everybody" shirts.

On Tuesday, McDaniel told ABC News Senior Congressional Correspondent Rachel Scott that the party was not trying to spite candidates who did not reach their requirements.

“They’ve got time for other debates and they can still continue to work towards California in September,” McDaniel said. “This has nothing to do with them. We just stuck to our rules.”

-ABC News' Kendall Ross, Gabriella Abdul-Hakim and Isabella Murray

Burgum’s debate appearance was in doubt after he suffered an injury while playing pick-up basketball with his staff.

Just hours before the start time, he announced he’ll be on stage after all.

His team is already fundraising off the incident, selling T-shirts with a silhouette of a cowboy hat-clad Burgum playing basketball -- a twist on the famous Nike Air Jordan "Jumpman" logo.

Earlier in the day, the governor was visibly emotional as he discussed the pain he was feeling with ABC News.

"I'm someone who's never taken prescription pain meds and I'm not doing that today. Even though people said that'd be a good idea. Because I’d rather … I mean so many Americans make so many sacrifices, think law enforcement, think of military, what they do for all of us," he said.

"I mean, if you're gonna lead this country, you got to be able to stand on one leg for two hours. You know, it's not, it's not 'Dancing with the Stars.'"

-ABC News' Alexandra Hutzler and Oren Oppenheim

As you watch the debate, keep an eye on which candidates separate themselves from the crowd. That’s because right now, the Republican presidential primary is not so much a race for first place as it is for second and third. FiveThirtyEight’s latest average of national GOP primary polls has Trump at 52 percent of the vote among likely Republican primary voters. DeSantis is a distant second at 15 percent, Ramaswamy is at 10 percent, Pence and Scott are at 4 percent, and Haley and Christie are at 3 percent. Everyone else is below 1 percent.

Trump’s lead will be very hard for the other candidates to close — so their best hope at this point is to stay in the game, in case Trump drops out (unlikely as that seems right now) or something else changes. DeSantis is currently in position to be the would-be front-runner if Trump drops out, but depending on debate performances and other factors, he could wind up in a close race with one of the other candidates currently clustered in that 5-10 percent range.

-Analysis by G. Elliott Morris of FiveThirtyEight

Chris LaCivita, a senior campaign adviser to Trump, said on the conservative “Ruthless” podcast streamed live before the debate that Trump does not currently plan to attend the second GOP debate, set for next month in California, but indicated that Trump could change his mind.

"He's not going to be in California ... Well, first of all, with President Trump, you know, he could change his mind at any moment … And you should just assume that he won't until he does,” LaCivita said.

Both fellow primary candidates and GOP officials have urged Trump to be on the debate stage, although some candidates have downplayed the significance of his absence.

-ABC News’ Laura Gersony

A hallmark of the American electoral process, debates are considered a key showcase for candidates seeking to hold the nation's top office.

Memorable moments include Ronald Reagan’s witty response to questions about his age and Kamala Harris’ challenge to Joe Biden on segregation and race, which prompted the viral line: "That little girl was me."

But not all debate highlights are positive. Richard Nixon’s sweating, Al Gore's relentless sighing and Rick Perry’s "oops" gaffe were considered costly to their campaigns.

"These are the only times we see them side by side," one expert told ABC News. "They provide opportunities for candidates to either help themselves or hurt themselves."

Read more here.

-ABC News' Alexandra Hutzler