Set aside the polls, the fundraising numbers, and President Trump’s name recognition as metrics of his early dominance of the Republican presidential contest. He has what could prove to be the most important advantage in the race: a leg up in winning the delegates needed to clinch the GOP nomination.

While the delegate count won’t begin taking shape until voting begins next January, Mr. Trump’s edge in the race to win their votes is years in the making. Many state Republican parties made changes to their rules ahead of the 2020 election by adding more winner-take-all contests and requiring candidates to earn higher percentages of the vote to claim any delegates.

Those changes all benefit a front-runner, a position Mr. Trump has held despite his mounting legal peril, blame for his party’s lackluster performance in the 2022 elections, and the turbulent years of his presidency.

As Mr. Trump makes another run for the White House, he has been focused on the looming battle for delegates, according to people with knowledge of his effort who requested anonymity to discuss strategy. He’s had regular discussions with state party chairmen, many of whose leadership races he got involved in, and has hosted delegations from Republican parties in Nevada, Louisiana, and Pennsylvania at his homes in Florida and New Jersey.

The moves are a sign of how Mr. Trump’s team is focused on the crucial, if less glamorous, aspects of winning the GOP nomination. That’s a notable change from his first bid for the White House in 2016 when his team of relatively novice operatives weren’t familiar with the minutia of the delegate contest and sometimes found themselves outflanked by better-prepared rivals, particularly Senator Cruz.

That doesn’t appear to be happening this time as election experts say it appears few other campaigns have been able to match Mr. Trump’s yearslong work.

“They’ve been asleep at the switch,” election lawyer Benjamin Ginsberg said.

More than 2,000 party activists, insiders, and elected officials make up the pool of delegates who will cast votes at the Republican National Convention next summer to formally select a nominee. The rules governing how delegates are selected are determined by state parties, which have until October to submit their plans for next year’s elections.

Many of the proposed changes that are starting to emerge in state parties appear to benefit the former president.

In Michigan, where the state GOP has become increasingly loyal to Mr. Trump, the party’s leadership this year voted to change the state’s longtime process of allocating all its presidential delegates based on an open primary election. Under a new plan widely expected to benefit Mr. Trump, 16 of the state’s 55 delegates will be awarded based on the results of a February 27 primary. The other 39 will be distributed four days later in closed-door caucus meetings of party activists.

Other Republican parties are looking to shift away from primary elections toward party-run caucuses, where Mr. Trump’s support among the party’s grassroots activists could put his rivals at a disadvantage.

In Idaho, one of the country’s most Republican states, a new law passed by the state legislature earlier this year eliminated the presidential primary process by moving the state elections to May as lawmakers tried to consolidate the voting calendar. The party’s state central committee decided last month to instead hold caucuses on March 2.

In Nevada, the state Republican Party is mounting a legal battle to try to hold a party-run caucus instead of a state-run primary election. The party chair, Michael McDonald, said he had spoken with Mr. Trump’s team about the process and ongoing lawsuit but had not heard from the campaign of his strongest rival, Governor DeSantis.

Other changes in the works would reduce the potential of any last-minute maneuvering at the convention.

At least two states, Louisiana and Colorado, are proposing changes this year that would bind delegates to vote for their assigned candidate during a second round of voting at the national convention in the unlikely event that no candidate has a majority on the first ballot.

Mr. Trump’s senior adviser, Chris LaCivita, said the campaign has had conversations with state parties all over the country about their delegate selection plans and is keeping close tabs on what its opponents are doing — or not doing.

As an example of the effort, Mr. LaCivita cited a single-day trip he made to Las Vegas in May to speak to a gathering of hundreds of Nevada Republicans.

“We are aggressive on every level and on every front,” he said. “We don’t let anything stand a chance.”

In 2016, Mr. Trump barreled his way to nab the GOP nomination despite his campaign being out-organized by Mr. Cruz’s team. When Mr. Cruz swept all 34 of Colorado’s delegates after a process in which party insiders voted at a series of caucus meetings, Mr. Trump wrote an op-ed complaining about a “rigged” system. He threatened to sue after the primary in Louisiana, where he won a greater percentage of votes, but Mr. Cruz was poised to pick up more delegates.

This time around, Mr. Trump is taking steps to cultivate ties with party insiders who might end up serving as delegates in 2024, making phone calls or, in some cases, schmoozing at big private dinners, like one he hosted in Iowa in May attended by the state’s attorney general, local lawmakers, and precinct organizers. A similar Trump reception in South Carolina saw 75 people, including state Governor McMaster, state legislators, and party activists, packed in a sweltering tent.

“From a tactical perspective,” Mr. LaCivita said, “Where we are today is leaps and bounds from where the campaign, a similar campaign, was in 2016.”

Mr. DeSantis has veterans from Mr. Cruz’s 2016 campaign working on his behalf.

The man who served as campaign manager to Mr. Cruz’s campaign, Jeff Roe, is advising Never Back Down, a super PAC supporting Mr. DeSantis’s campaign, but the organization is not involved in delegate strategy and is not currently planning to be, according to a person familiar with the effort who wasn’t authorized to disclose internal strategy.

The political director of Mr. DeSantis’s campaign and another veteran of Mr. Cruz’s 2016 bid, Sam Cooper, said the Florida governor’s team is closely monitoring developments in the states around delegate selection plans.

The DeSantis campaign is working to identify local party activists who could serve as delegates but also is specifically courting state lawmakers, who are typically active in their local GOP groups.

“They’re surrogates for us on the ground,” Mr. Cooper said. “But also they’re close to the process.”

The campaign boasts that more than 250 state lawmakers have endorsed Mr. DeSantis. The governor himself is very involved, Mr. Cooper said and speaks to legislators directly either in one-on-one calls or, as he did in June, in a Zoom call with more than 100 lawmakers around the country.

Mr. Cooper noted that Mr. DeSantis has made his own trips to speak before state and local GOP officials, appearing at ten events in eight states since March and headlining fundraisers for Republican groups.

The DeSantis campaign declined to specify any states where the campaign provided feedback on a delegate selection plan, but Mr. Cooper said the campaign feels “very good about the map.”

“We haven’t seen a state party or a state make a move that’s so off the wall that could only support one candidate or the other,” he said.

One potential opening for a challenger like Mr. DeSantis could be California, which has 169 delegates to dole out, more than any other state.

Thanks to changes passed by Democrats at the state Capitol, California’s primary contest will be on March 5, requiring the state GOP to change its delegate plan in order to comply with national GOP rules for early contests.

The changes, which the state’s Republican Party is set to consider and approve late this month, are set to award delegates proportionally to the candidate’s share of the vote rather than award all delegates to the winner.

That could give a candidate trailing in second place a chance to make up ground — especially someone like Mr. DeSantis, who has made a point of campaigning in the state.

The chief operating officer and executive director of the California GOP, Bryan Watkins, said the organization has been in touch with Republican campaigns about the proposed change.

“As the state with the most delegates in the country, the CAGOP wants California to be a place where Republican presidential candidates will invest their time speaking to our voters and earning their support,” he said in a statement. “So we appreciate the campaigns’ feedback and perspectives on the best way to accomplish that goal.”