Sen. John McCain (R-Ariz.) will endorse former Massachusetts governor Mitt Romney’s (R) presidential bid on Wednesday, BuzzFeed’s Ben Smith reports.

Sen. John McCain (R-Ariz.). (Chip Somodevilla/Getty Images)

A McCain spokesman did not immediately respond to a request for comment early Wednesday morning.

News of the endorsement comes as Romney stands poised to come in first or second in the Iowa caucuses, outperforming expectations in a state where four years ago he struggled to round up support. As of early Wednesday morning, Romney was locked in a tight race with former Pennsylvania senator Rick Santorum (R) for the top spot in what looks to be one of the Hawkeye State’s closest nominating battles ever.

Polls show Romney with a more than 20-point lead in New Hampshire, which holds its first-in-the-nation primary on Jan. 10. If he wins both Iowa and the Granite State, he will become the GOP’s first non-incumbent candidate in history to do so.

That the GOP’s 2008 standard-bearer and Romney’s onetime fierce rival would come out so swiftly in support for Romney – one day after the first nominating contest of the cycle – is a testament to the strength of Romney’s Tuesday performance. It’s also a sign that the GOP establishment is falling in quickly behind his campaign, likely in the hope of heading of an extended (and potentially damaging) primary fight.

View Photo Gallery: In December, the GOP presidential candidates turned their attention to Iowa and saw the field grow smaller as one candidate suspended his campaign.