Protestors chant in Manhattan, where the three GOP presidential candidates were to speak at the Grand Hyatt on Thursday. (Photo by Jabin Botsford/The Washington Post)

Stung by a week of criticism by Donald Trump, the Republican National Committee officials swung back at the party's presidential front-runner on Friday, reminding him that rules for selecting convention delegates have been on the books since last fall.

The party's rebuke comes as Trump and his top aides have used interviews, campaign rallies and newspaper op-eds this week to criticize what transpired last weekend in Colorado, where state Republicans held a convention to select their 34 delegates to the Republican National Convention in July. Sen. Ted Cruz (R-Tex.) swept the contest, and Trump failed to have any of his supporters win delegate slots.

"One million Republicans in Colorado were sidelined" by the party's decision to hold a convention instead of a caucus or primary," Trump wrote in an op-ed published Friday by the Wall Street Journal.

"In recent days, something all too predictable has happened: Politicians furiously defended the system," Trump wrote. "'These are the rules,' we were told over and over again. If the 'rules' can be used to block Coloradans from voting on whether they want better trade deals, or stronger borders, or an end to special-interest vote-buying in Congress -- well, that’s just the system and we should embrace it. Let me ask America a question: How has the 'system' been working out for you and your family?"

Early Friday, RNC communications director Sean Spicer sent reporters a memo stating: "For decades, this grassroots-driven, democratic process has been transparent and effective. This cycle is no different."

"The rules surrounding the delegate selection have been clearly laid out in every state and territory, and while each state is different, each process is easy to understand for those willing to learn it," Spicer said. "It ultimately falls on the campaigns to be up to speed on these delegate rules. Campaigns have to know when absentee ballots are due, how long early voting lasts in certain states, or the deadlines for voter registration; the delegate rules are no different."

The back-and-forth comes just as the party heads into another busy period of delegate allocation and selection. This weekend, seven states will hold meetings to select at least some of their delegates to the Cleveland convention. Republicans will gather in Georgia, Kansas, Oklahoma, South Carolina and Virginia for meetings in congressional districts to award their delegates.

In Wyoming, Republicans are hosting a convention similar to the one held in Colorado, and Trump is again poised to lose to Cruz.

On Tuesday, the New York primary will award 95 delegates. On April 26, Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island will award a combined 172 delegates.

The decision on when, where and how to award delegates is "driven by grassroots voters across the country," Spicer wrote.

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