After a dozen debates, millions of votes and countless television ads, the Republican presidential race moved to a church gym on Thursday as the struggle to reach the finish line disappears into backrooms and dark corners.

Sitting on folding chairs in a brightly lit, sparsely decorated gym next to Seventh Day Adventist church in suburban Denver, party activists spent four hours after work listening to close to 100 speeches and choosing three of the 2,472 delegates to the Republican national convention in July.

This is party politics at its most granular and mystifying. Most delegates are chosen in primaries or caucuses where individual voters show up and register their preference for the party’s nominee on a ballot.

But in Colorado as well as Wyoming and North Dakota, voters have no say in the matter. Instead, party activists meeting in hotel ballrooms and church gymnasiums have that power. In these states, delegates are elected through an indirect process that culminates in congressional district and state conventions where party activists elect delegates to Cleveland. This is a process that is about organization, planning and strong grassroots support – and it’s one where Ted Cruz is excelling.

The biggest prize of these three states is Colorado, which sends 37 delegates to Cleveland. Each of Colorado’s seven congressional districts sends three delegates apiece to the convention while the state convention sends 13. North Dakota, which sends 28 delegates to the convention, held a raucous, confused affair last week where Cruz got a plurality of the delegates available. In Wyoming, 12 delegates were awarded in county conventions in early March and the remaining 17 will be elected at a state convention next weekend.
Just like the national convention in recent years, these delegate contests had long been considered academic, internal party affairs. However, with the growing likelihood of a contested convention where no candidate receives the 1,237 delegates to clinch the nomination, they have become vital affairs as campaigns claw for every possible delegate.

At Thursday’s convention in Colorado’s seventh congressional district, a Democratic-leaning area in suburban Denver, Cruz won all three delegates. The Texas senator ran a well-organized effort, his campaign having organized in the state for at least a year and building an official slate of delegates who not only were pledged to Cruz on the first ballot, but who they thought would stay true to him in a contested convention. Their slate included well-known activists and George Athanasopoulos, who was running for Congress in the district.

The campaign didn’t just use old-fashioned politicking; it supplemented with data modeling to better target and identify delegates. Further, both the influential gun rights group Rocky Mountain Gun Owners and the Republican National Coalition for Life were handing out delegate slates – and both were almost identical to the official Cruz slate.

The only problem Cruz had was that too many of the nearly 60 candidates for delegates at the convention supported him. Delegates could run either as unpledged and be free on the first ballot, or pledge themselves to support one of the Republican candidates. Repeatedly, delegates came up and insisted that even though they weren’t on the official Cruz slate, they would vote for him. Twelve candidates were formally pledged to the Texas senator.

In contrast, the Trump campaign was disorganized. Former state director James Baker was fired earlier in the week; his replacement, Patrick Davis, just started on Tuesday and Trump supporters had little contact with the campaign. Stacy Clark-Sacks, a Trump supporter who wasn’t a delegate to the district convention, said that there was no organization in Colorado. Instead, “there are a very select few of us who have been doing social media and we know a lot of each other”. She bemoaned before the convention started: “I don’t see him having the type of support he needs here.”

But Trump’s loss wasn’t just due to lack of support. The slate cards that his campaign handed out featured three candidates for delegate. In his brief remarks Davis hailed those listed as “the three delegates who will be loyal to Donald Trump at the convention”. The problem was that two of them weren’t listed on the ballot. When Davis was asked afterward how this happened, he simply said: “That’s a very good question.” He later said it had been “an administrative snafu”.

However, these flawed slate cards were still an improvement. Davis noted that at Colorado’s two district conventions last weekend, there weren’t even slate cards. He said the campaign didn’t have the “sophistication” at the time. (Needless to say, in those two congressional districts Cruz won all six delegates.)

Four more congressional districts will hold conventions on Friday and the state convention will be on Saturday.

Trump has already virtually conceded Colorado, cancelling a planned visit to the Rocky Mountain State, and his campaign has long braced itself to be shut out there. Cruz is scheduled to appear on Saturday but Trump’s surrogate will be a campaign staffer, senior policy adviser Stephen Miller. In contrast, Trump sent Dr Ben Carson to North Dakota’s raucous state convention last week and is scheduled to send Sarah Palin to Wyoming’s convention next week.

The campaign of the Ohio governor, John Kasich, which ran an “open convention slate” without the candidate’s name in the seventh congressional district, will have former New Hampshire senator John E Sununu appearing on his behalf.

The winners may may not make victory speeches, but this inch-by-inch trench warfare could be all-important come July in Cleveland.