MITT ROMNEY: Donald Trump won't win the GOP nomination

The Republican Party's 2012 presidential nominee isn't hot on real-estate mogul Donald Trump's chances in the 2016 race.

Mitt Romney, speaking at the Washington Ideas Forum on Wednesday, was asked if he would support Trump should he win the GOP primary.

"I will support the Republican nominee. I don't think that's going to be Donald Trump," he replied.

He was pressed to elaborate on his response.

"My party has historically nominated someone who's a mainstream conservative and someone who has a foundation in foreign policy that gives people confidence that they can guide the ship of state in troubled waters," Romney continued.

The former Massachusetts governor went out of his way to secure Trump's endorsement in 2012, but the two have butted heads during this year's contest.

Romney criticized Trump for panning Sen. John McCain's (R-Arizona) war record, while Trump has bashed Romney for losing his race against President Barack Obama.

As far as who might qualify as a "mainstream conservative" in the 2016 field, Romney cited New Jersey Gov. Chris Christie (R), Sen. Marco Rubio (R-Florida), Ohio Gov. John Kasich (R), former Florida Gov. Jeb Bush (R), Sen. Lindsey Graham (R-South Carolina), and former Hewlett-Packard CEO Carly Fiorina.