Donald Trump has made his first threat to sue over the procedures for selecting delegates to the Republican convention. It surely won’t be his last.

The Wall Street Journal reported that Ted Cruz may come out of Louisiana with as many as 10 more delegates than Trump, even though the mogul narrowly beat Cruz in the popular vote there. In a tweet, Trump pronounced it “unfair,” and worthy of litigation.

The Louisiana delegate picture isn’t evidence of anything untoward. Trump and Cruz both won 18 delegates on election night. Marco Rubio, since dropped out, won five, and another five are uncommitted. The Cruz campaign has done the nitty-gritty work to see that those delegates are likely Cruz supporters.

The only scandal here is that the Cruz campaign, built on grass-roots organizing muscle, knows the process and is working hard for every advantage. Trump’s plaint is a little like showing up at a cricket match and crying foul because the opposing team knows the rules and all you know is that you swing a bat.

The Louisiana flap is a window into the intricate, state-by-state process of picking delegates to a convention in Cleveland where the allegiance of every last delegate might matter. If there is an open convention, Trump will argue that the voters should rule, not delegates no one has heard of, selected at obscure precinct, county, district and state meetings. He will, in short, declare the entire exercise of a contested convention illegitimate.

Is it? We are used to the voters directly deciding, and should Trump perform strongly enough to win a majority of delegates, 1,237, they, in effect, will. But if he falls short, the delegates enter the picture.

The requirement for a majority of delegates (Trump once decried this rule as arbitrary) is meant to ensure that the nominee is, as much as possible, the consensus choice of the party. Ordinarily, this isn’t an issue — the early leader in a nomination fight vanquishes the opposition and steadily consolidates the support of the party.

In 2012, Mitt Romney didn’t lose a contest after March 24. His closest competitor, Rick Santorum, dropped out shortly after losing Wisconsin on April 3, and after that, Romney was racking up victories with 60 percent of the vote or more.

For Trump — who spent last week threatening and mocking Ted Cruz’s wife — this unifying march down the homestretch is hard to imagine. If Trump has only won a plurality of delegates, it won’t be a sign of strength, but of weakness. A badly divided party would be nominating a candidate who couldn’t reach a majority and, so far, has shown no general-election appeal. In this circumstance, delegates would be justified in looking to someone else better suited to win an election and protect the party’s interests.

It’s not unheard of for top vote-getters in America to fall short of the top prize. Otherwise, there would have been a Gore administration. Al Gore won the popular vote in 2000, but still fell short of George W. Bush, who won the Electoral College.

If you count Michigan, where Barack Obama’s name didn’t appear on the ballot, Hillary Clinton very narrowly won the most votes in the 2008 primaries. That was good enough for an appointment as secretary of state — under President Obama, who understood the delegate-allocation rules much better.

Trump has thrived so far without an extensive, traditional political operation. But politics isn’t only about TV interviews and big rallies. There is a reason that the system also rewards candidates who can motivate and muster people to do the grass-roots activism involved in winning small victories at local meetings. This is literally getting people involved in the process, and it could take on an outsized significance in deciding the immediate future of the Republican Party.

Trump would be well-served to complain less about the rules, and learn more.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.