Republican Romney opts out of 2016 run for president

Romney's decision helps clarify an emerging Republican field split between potential establishment candidates like former Florida Governor Jeb Bush and conservative voices represented by Texas Senator Ted Cruz and former Arkansas Governor Mike Huckabee.

The move will likely boost Bush, the brother of former President George W. Bush and son of former President George H.W. Bush, even though Romney has privately made known to aides he is not convinced that Bush can defeat Hillary Clinton if she becomes the Democratic presidential nominee.

But Romney's decision also helps other potential candidates such as Florida Senator Marco Rubio, who was on Romney's vice presidential short list in 2012; Wisconsin Governor Scott Walker and New Jersey Governor Chris Christie, all of whom will have a better chance for money and media attention with Romney on the sidelines.

The former Massachusetts governor felt he would win the Republican presidential primary, a former adviser said. But Romney did not think he would present a sufficient "new versus old" contrast for the battle against Clinton, the former first lady, New York senator and secretary of state, who is the early favorite for the Democratic nomination.

"He thinks Jeb would be a perfectly credible nominee but that there are others who might be able to hold up that 'new versus old' banner a little better," the former adviser said, speaking on condition of anonymity.

"After putting considerable thought into making another run for president, I’ve decided it is best to give other leaders in the party the opportunity to become our next nominee," Romney said in his statement.

He made clear he felt he would be able to raise enough money for a campaign, rejecting a narrative that has grown in recent days as some major 2012 fund-raisers expressed concern about another Romney run.

Those fund-raisers said that since Romney opened the door to a possible candidacy three weeks ago, he had not made clear how his message and inner circle would improve in 2016.