Opinion: Super Tuesday won’t help Haley. But she can help Trump.

Editor’s note: Daniel McCarthy is the editor of Modern Age: A Conservative Review and a columnist for The Spectator World and Creators Syndicate. The views expressed in this commentary are his own. View more opinion at CNN.

If practice makes perfect, Nikki Haley is only making Donald Trump stronger by dragging out the race for the Republican nomination.

The former US ambassador to the United Nations has no realistic path to becoming the nominee, losing almost every primary to date by wide margins. Yet she doggedly remains in the race and is on the ballot in Super Tuesday’s 15 GOP primaries and caucuses.

Her ability to draw double-digit support in key early primaries — and indeed to win in Washington, DC, over the weekend — is annoying and even a little embarrassing for Trump. The former president no doubt hopes she’ll drop out after he cleans up Tuesday night, and his campaign predicts that it will have won enough delegates to clinch the nomination by March 12. But there’s been an upside for him to Haley’s tenacity: Her challenge is helping to prepare him for the showdown with President Joe Biden in the fall.

Merely token challengers, such as Biden’s opponents in the Democratic race — US Rep. Dean Phillips of Minnesota and author Marianne Williamson — provide little exercise for a front-runner’s campaign. The Michigan primary last week revealed just how little Phillips and Williamson matter: Each received no more than 3% of the vote, while the “uncommitted” line on the ballot took more than 13%

There is discontent with Biden in the Democratic Party, but no one running against him is in a position to marshal it against him — or give him the kind of run for his money that could elevate his game.

Haley, on the other hand, is well-financed and well-suited to capitalize on disaffection with Trump, both within the GOP and among whatever independent or even Democrat-leaning voters she can motivate to participate in the Republican contest. She may not be able to win, but she can give Trump a workout.

For his campaign, a prolonged primary season means more experience with mobilizing supporters, maximizing turnout not just to win but also to win as decisively as possible.

In 2016, Trump was put through his paces by Ohio Gov. John Kasich and Sen. Ted Cruz of Texas, who both stayed in the race until May. Like Haley, they were strong contenders, even though they, like her, had no plausible shot at the nomination after Trump’s early victories in New Hampshire and South Carolina.

The Republican contest that year was longer and messier than the Democratic race between former Secretary of State Hillary Clinton and Sen. Bernie Sanders of Vermont, and then as now, there was speculation about what that division in the GOP would mean for the party’s prospects in November. Yet Trump prevailed over Clinton.

He was no doubt helped by the hard-fought primaries, which are an invaluable learning opportunity for campaigns. They reveal a candidate’s weaknesses, while there is still time to overcome or mitigate them.

To start with, who are the Republican voters that Trump will have the most trouble getting to the polls in November? Haley’s performance provides the answer. In New Hampshire, for example, exit polls showed that Trump underperformed among married voters, who made 65% of those surveyed: He won 50% of them to Haley’s 47%, compared with his commanding 63% to 35% win among the unmarried.

And if it’s no surprise that Republicans who recognize Biden as the winner of the 2020 election are among the GOP demographics that are least likely to support Trump, it’s nonetheless important for his campaign to know just how big that demographic is. In South Carolina, it was 36% of voters in the Republican primary (and Trump won 18% of them). In New Hampshire, it was 46% (and Trump won 22% of them).

In this way, bad news can be as valuable as good news where developing strategy is concerned. In South Carolina, 81% of the Haley voters surveyed by exit polls said they were casting their ballots against Trump rather than for Haley. His prospects of winning over those voters in the general election are bleak, unless his campaign’s messaging to them de-emphasizes Trump himself and instead focuses on Biden — perhaps by painting Biden in colors that make him resemble what Haley voters dislike about Trump.

Of course, exit polls in a contested primary also tell Trump what segments of the party are most enthusiastic about him, and mobilizing those voters to the utmost will be necessary in November. Biden won four of 2020’s battleground states by 2% or less, and Trump won North Carolina, the closest battleground state in which he prevailed, by just a little over a point. Margins in 2016 battlegrounds were similarly narrow. Although nothing in politics is as obvious as the need to turn out one’s base, actually doing so requires recent, reliable information of the kind that primary contests provide — and it’s a help if voters have already put themselves in a participatory mindset by going to the polls in a primary. Voting is a habit.

Trump’s glide to the nomination isn’t threatened by Haley’s continuing campaign. Her effort isn’t harmless, however: It does force the Trump campaign to spend money that could otherwise be put toward taking on Biden. But that harm is likely outweighed by the benefit Trump’s campaign receives from putting its resources into voter identification and turnout. The primaries are a dry run for the general election, and the more Trump perfects his get-out-the-vote operation now, the more formidable he’ll be in the main event.