Republicans stumbled in their unity efforts Tuesday afternoon by unnecessarily infuriating Ron Paul supporters with a new party convention rule to limit the delegate count of insurgent candidates.

Mr. Paul received 190 delegate votes, versus more than 2,000 for Mitt Romney. But on the convention floor the Paul supporters were seething as they booed loudly and shouted "shame" over the new rules to create an acclamation for the nominee. The GOP leaders said the rule is intended to bind delegates to their commitment based on...