Donald J. Trump got crushed at the Colorado Republican state convention, where Ted Cruz swept the national delegate selection.
This sweep happened not because the convention was rigged, but because Trump did a horrible job of working the caucus process that led to the convention. Trump all but ignored the electoral process leading up to the convention, and didn't even bother to go make a pitch himself at the convention, unlike Cruz who gave a speech on stage as Trump surrogates were furiously working to convince delegates to vote for Trump.
Throughout the process, there was no discernible complaint by Trump and his supporters so long as they thought they had a shot at winning, or at least eating into Cruz's likely win.
Only after it was over, and Colorado together with Wisconsin created momentum for Cruz, did Trump and his supporters start alleging fraud and deceit. This was a classic "change the narrative" Trump ploy, much as he would roll out high-profile endorsements that morning after a debate.
Had Trump done better, there would not have been a peep. This controversy is not about principle, fairness or anything other than Trump losing and fearing his chance to win on a first ballot is slipping away.