DENVER — (CNN) Ted Cruz’s resounding win in Colorado’s GOP contest this weekend provided fresh evidence that Donald Trump’s campaign is still scrambling to catch up in the state-by-state delegate hunt.

But the Trump campaign’s threat that they might challenge the Colorado results at the Republican National Convention showed something else: Their campaign is gearing up for battle in Cleveland — and no error will go unnoticed.

The debate over the national delegate selection in Colorado this weekend qualified as the very definition of inside baseball.

But that is the game that the GOP campaigns will be playing at the convention if no candidate reaches the 1,237 delegates needed to clinch the nomination before Cleveland.

By Sunday, the Trump campaign had voiced a litany of complaints about Colorado’s complex process, even though it was obvious on the ground that they had not done the aggressive leg work to court Colorado delegates that the Cruz team had done.

“I win a state in votes and then get non-representative delegates because they are offered all sorts of goodies by Cruz campaign. Bad system!” Trump tweeted Sunday.

Later in the day, Trump took to Twitter again to protest the fact that Colorado did not hold a primary or a caucus, due to costs, and inside used arcane party rules for choosing delegates.

“How is it possible that the people of the great State of Colorado never got to vote in the Republican Primary?” Trump tweeted Sunday evening. “Great anger – totally unfair!”

He also retweeted a link to a Facebook post where one of his supporters burned his Colorado Republican Party registration over anger at the process at the Colorado state convention.

Then he declared: “The people of Colorado had their vote taken away from them by the phony politicians. Biggest story in politics. This will not be allowed!”

On NBC’s “Meet the Press” Sunday, Trump’s new convention manager Paul Manafort accused the Cruz campaign of using “Gestapo tactics” to wrangle delegates.

Cruz campaign spokeswoman Catherine Frazier said the campaign had won “because we’ve put in the hard work to build a superior organization,” dismissing the complaints as sour grapes.

But it was the threat of a convention challenge over the ballot problems in Colorado this weekend that is the kind of legal spat that could lead to campaign-on-campaign legal warfare at the convention.

If a campaign alleges that delegates were elected improperly, those challenges can be heard by the credentials committee, which decides whether the delegates in question will be allowed on the floor to vote.

In a race that could be decided by handful of delegates those challenges could be a pivotal part of the nomination process this cycle.

To the casual observer of politics, the details of what went awry for the Trump campaign in Colorado Springs might seem like an irrelevant debate over minutia. National delegate ballot positions, to be exact.

Ballot positions were assigned to more than 600 people who ran for the final 13 delegate slots at the GOP convention on Saturday.

To narrow the field, each presidential campaign printed up slates listing the national delegate candidates that they had endorsed. Those slates were handed out by volunteers at the convention.

But the slates put out by the Trump campaign contained numerous errors when it matched names to ballot numbers. At the Congressional District 7 convention Thursday night where three convention delegates were selected, the slate printed by the Trump campaign contained the names of two delegate candidates supporting Trump who weren’t even running in that district.

On the first slate printed by Trump campaign for Saturday’s election — which detailed the names and ballot numbers of 26 people who were running to be Trump delegates at the convention — more than a half dozen names were listed with inaccurate ballot numbers.

If you were a Trump supporter at the convention hoping to support his slate of delegates that mattered — a lot — because the paper ballots that attendees used to cast their votes late Saturday afternoon contained only numbers, not the names of each delegate candidate.

The Trump campaign printed a second slate that was meant to correct the corresponding numbers and names that were wrong on the first slate. But there were mistakes on the second as well.

The campaigns of Cruz and Ohio Gov. John Kasich did not have the same problems — suggesting that the mistakes could have amounted to printing errors by the Trump campaign on their slates.

But the ballot distributed by the state party did include at least one clerical error: There was no bubble on the ballot for delegate candidate #379 (who was running as a Trump delegate, according to the state party list). Instead in the spot where #379 should have appeared, there was a second bubble for #378 (who was running as an unpledged delegate).

Another wrinkle: Inside the convention program printed by the state party, the list of candidates running for the 13 national delegate slots (and their corresponding ballot numbers) only went up to #588, even though there were 619 candidates.

The state GOP printed a supplemental ballot and placed the names and ballot positions of the remaining candidates on two screens above the stage, but Trump supporters said that not every attendee got one.

Beyond that, the Trump campaign said a number of their potential national delegates had their ballot positions changed. Others, Trump advisers said, filed the proper paperwork but never ended up on the ballot.

“We’re not taking a credential challenge off the table,” said Trump adviser Alan Cobb. “It’s something we’ll be looking into over the next few months.”

A spokesman for the Colorado GOP said party officials were looking into whether there were problems with the ballot.

But it’s clear the Trump campaign is not going to be dismissing these issues anytime soon.

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