Having started with just a few dozen delegates, organizers also said Sunday that they now count several hundred delegates and alternates as part of their campaign. . . .

The group is led by delegates seeking to block Trump at the GOP convention next month in Cleveland by changing party rules so that they can vote however they want — instead of in line with the results of state caucuses and primaries. It is quickly emerging as the most organized effort to stop Trump and coincides with his declining poll numbers.

Concerned Republicans also are increasingly alarmed by Trump’s rhetoric, including his racial attacks on a federal judge, a fresh call made Sunday to begin profiling Muslim Americans, and his support for changing the nation’s gun laws in the aftermath of a mass shooting in Orlando.