In his short time at the Capitol, Senator Ted Cruz, a freshman Republican from Texas, has shown little regard for long-standing rules of decorum. But on Friday, he publicly discussed the closed-door dealings of the Senate Republican Conference — and trashed his colleagues in the process. Stopping by a Texas meeting of the Tea Party-aligned group FreedomWorks, Mr. Cruz called many of his colleagues “squishes,” forced to stand on conservative principles by the uncompromising stands of a triumphant trio of Republican “constitutionalists”: himself and Senators Mike Lee of Utah and Rand Paul of Kentucky. At stake was the gun control...