Donald Trump repeated his threat over the weekend to sue Ted Cruz if the senator from Texas doesn't "take down his false ads and retract his lies" against the businessman. Cruz, battling him for the lead in South Carolina, has run ads drawing attention to Trump's use of eminent domain while a super PAC backing Cruz has slammed Trump by suggesting that he supports Obamacare. Trump also lumps in Cruz's mailers in Iowa and the other parts of Trump's "I really won Iowa" platform.

But that's all an excuse for Trump to talk about whether Cruz is constitutionally eligible to run for the presidency given his Canadian birth, an issue that Trump keeps threatening to force by filing a lawsuit. Which leads to three different questions that are worth answering:

1. Can Trump sue Cruz?
2. If he does, will the courts throw it out?
3. If they don't, can Trump win?

The answers:

1. Can Trump sue Cruz?

Answer: Sure.

Pretty much anyone can sue anyone else for anything. It's why you get weird lawsuits from prisoners targeting President Obama or a blind barber suing to be reinstated at his job.

Trump knows full well that you can sue nearly anybody at any time, because he does it often. Trump has sued Univision, Palm Beach County over the airport there, celebrity chef José Andrés, TV host Bill Maher and even Trump Entertainment Resorts. The first three of those lawsuits were brought since Trump became a candidate. Our goal here isn't to adjudicate each and every one of those cases but merely to establish a pattern.

There's value to Trump in merely filing these suits. Suing Univision for $500 million after the media company balked at partnering with him on the Miss Universe pageant demands headlines — and the half-billion dollars he requested draws attention. As is often the case, the two parties settled out of court with the details of the settlement not known. Maybe Trump got $100 million. Maybe he got nothing. Whatever else he got, he got publicity and planted a flag on the issue — which is why he does it.

2. If he does, will the courts throw it out?

Answer: Not necessarily.

That Univision lawsuit didn't end up going to trial. If Trump really wants to stop Cruz's candidacy, though, his lawsuit almost certainly would.

At that point, the question becomes one of standing. While nearly anyone can sue nearly anyone else for nearly anything, the courts must first determine whether the plaintiff (the person filing the suit) has a legally defensible argument for why the defendant (the person being sued) owes the plaintiff something (money, a change of behavior, etc.). This is called standing. For example, if a drunk driver crashes into your neighbor's house, you can't sue the drunk driver because you weren't involved. You didn't have standing to sue. The neighbor whose house was damaged, though, almost certainly does. (Some legal wiz is going to write in and point out some obscure statute under which the particular scenario I offer is incorrect, and God bless him for doing so. This is why lawyers make so much: They can find such exceptions.)

The courts would try to decide whether Trump has standing to sue Cruz over his eligibility. As neatly articulated by election-law expert Rick Hasen, he probably does.

There is precedent in the law suggesting that a candidate running against someone ineligible to hold office can argue that he is being harmed by that ineligible candidate. For example, if Cruz were 10 years old (and therefore obviously ineligible to be president, since the Constitution says you must be 35) but were still on the ballot, little tween Cruz would be peeling votes from other candidates. If Sen. Marco Rubio of Florida beat Trump by 10 votes in South Carolina and Cruz got 15 votes from people who would otherwise have voted for Trump, Cruz's ineligible candidacy negatively affected Trump.

Hasen points to several examples of past cases that rotated around this issue. Among the most interesting is the evocatively titled Drake v. Obama, which does not center on the Canadian hip-hop artist. Instead it involved (the also evocatively named) Wiley Drake who ran for vice president on the American Independent Party ticket in 2008. He and a number of other parties sued Barack Obama, claiming that the president was ineligible to hold office based on his birth. A district court found that Drake and his running mate, Alan Keyes, had standing to sue — based in part on a similar suit brought against Sen. John McCain (R-Ariz.) — but a higher court noted that the lawsuit was filed after the election was over.

Trump, Hasen writes, "is a serious candidate, who faces a potential loss of election to Cruz. He’s not a write-in candidate who’s just trying to conjure up standing. He faces a real injury." Therefore, he figures, Trump would probably be determined to have legal standing.

3. If the courts don't throw the case out, can Trump win?

Answer: Probably not.

Determining that Trump can sue is not the same as determining that Cruz has negatively affected Trump's campaign. Remember: Trump wouldn't be suing over the various slights he alleges he has experienced by Cruz's campaigning (slights which, in my estimation, have affected Trump's success only slightly above zero percent). He's suing to question whether Cruz is constitutionally eligible to hold the presidency, or if he meets the "natural born citizen" requirement articulated under the Constitution.

As we've noted before, legal experts broadly — but not universally — agree that Cruz can indeed serve as president. Under U.S. law, he was a citizen at birth, by virtue of being born to an American citizen, despite that birth having taken place in Canada.

But is "citizen at birth" the same as "natural born citizen"? Again, most legal scholars think the answer is yes. But the caveats and footnotes and hypotheticals are nearly endless — in part because the courts have never weighed in on this issue before. It can be hard to predict what the courts will do!

If this ever goes to court, it seems unlikely that Trump will actually sue Cruz (assuming that Trump wins South Carolina). Trump's litigiousness is rooted in part on knowing that he can settle most lawsuits out of court as he sees fit; this case would be such a massive event that it could end up being harder for Trump to resolve as he sees fit. The threat of a lawsuit, too, can be an effective tool for changing behavior, which Trump also knows very well.

Or maybe this case will end up in front of an eight-person Supreme Court split along partisan lines, right before the next inauguration! Wouldn't that be fun?