Republicans are denouncing President Obama's latest delay on the Keystone XL pipeline, six long years after it was proposed. But for cold political fury they have nothing on Terry O'Sullivan, who runs the Laborers' International Union that represents a half-million construction workers.

"This is once again politics at its worst," Mr. O'Sullivan said in a public statement that deserves to be quoted at length. "In another gutless move, the Administration is delaying a finding on whether the pipeline is in the national...