Published: Jan 04, 2012 7:19 AM EST
Updated: Jan 04, 2012 5:22 PM EST

DES MOINES, Iowa (AP) — A Republican official says that 2008 GOP nominee John McCain is endorsing Mitt Romney for the party's 2012 nomination.

The official was not authorized to speak publicly about the endorsement and requested anonymity to discuss it.

The official says McCain's endorsement is scheduled to be announced Wednesday.

The endorsement is a signal by the GOP's one-time standard-bearer that Republicans should start falling in line behind the former Massachusetts governor.