With this 77-second ad, the Great Republican Proxy War of 2018 has officially begun.

As usual with proxy battles, the players and allegiance and strategies can be a bit confusing. So let's run down what's so significant about this ad and why, even if you're not an Arizona Republican, you should care about it.

The battlefield: Arizona, specifically the state's Senate GOP primary in August 2018.

The players: Sen. Jeff Flake is running for a second term and is facing multiple challengers from within his own party, including former state senator Kelli Ward, who unsuccessfully tried to unseat Sen. John McCain (R) in 2016.

Their armies: On Flake's side is pretty much the entire Republican establishment. Senate Majority Leader Mitch McConnell (R-Ky.) is determined to keep Flake in his seat.

On Ward's side is none other than the president of the United States and his billionaire allies. Trump is incensed that Flake wrote a book blaming his party for the rise of Trump and breaking down a case against the president. “To carry on in the spring of 2017 as if what was happening was anything approaching normalcy required a determined suspension of critical faculties,” Flake writes, “and tremendous powers of denial.”

Never one to let slide a public slight, Trump soon afterward tweeted his support for Ward in the primary. He has openly considered spending $10 million of his own money to unseat Flake, and a pro-Trump donor recently wrote a Ward super PAC a $300,000 check.

The battle plans: Get ugly.

Trump is heading to Arizona on Tuesday for a rally, where some expect him to trash Flake. And it's not out of the question that he'll endorse Ward. (Trump won Arizona by 3.5 points in November and easily won the GOP primary.)

Here's where the “Chemtrail Kelli" ad comes in. Hours before Trump is scheduled to appear in Arizona, a McConnell-allied super PAC released the scathing ad, which attacks Ward and her “crazy ideas" in an attempt to show that she's on the fringe of the Republican Party — and to keep her there.

The main line of attack: In 2014, as a state senator, Ward called a public hearing to talk about her constituents' concerns that passing jets' condensation was really chemicals the government was surreptitiously spraying on their community. It's a conspiracy theory, and Ward later said she doesn't believe in chemtrails.

Except, you wouldn't know that from watching the Senate Leadership Fund ad.

“Ward wasted your tax dollars for a town hall on chemtrail conspiracy theories," the narrator says a few seconds in. Also, the ad calls her “Chemtrail Kelli" about a dozen times.

Ward isn't above fighting dirty, either. When she was challenging McCain, she launched one of the nastiest primary attacks we'd ever seen. On McCain's 80th birthday, Ward went on cable news and called him “weak" and “old" and not-so-casually dropping that the average life expectancy of a man today is “less" than 86, the age McCain will be at the end of his next term.

McCain has since been diagnosed with brain cancer. After his diagnosis was announced in July, Ward said in a radio interview that she hoped his family would advise him to “step away as soon as possible."

Why you should follow this battle: It's the most tangible split yet between Trump's camp and the rest of the Republican Party. Up until now, the two sides have had a few sparring matches — lawmakers tweeting their disappointment in Trump over how he handled the unrest in Charlottesville, for example, or Trump dissing McConnell on Twitter.

But the Senate proxy battle in Arizona is much more than words. Both sides are throwing insults and money at each other, seemingly in unlimited supply. And it's probably only going to get uglier and involve even more of Washington as it does. What happens in this Senate primary is definitely not staying in Arizona.