Larry Sabato reacted on "Happening Now" just minutes after Mitt Romney announced that he will not run for president in 2016.

"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, adding that he is "convinced" he could win the nomination.

Sabato said the announcement is not a surprise because Romney had been testing the waters in recent weeks and "found them to be chilly."

He said many powerful donors and former staffers were opposed to Romney running again or lining up with other candidates.

"Romney could only go down as the campaign progressed. He was unlikely to be the nominee," said Sabato. 

Jon Scott asked about the latest Fox News poll, which put Romney ahead of the potential GOP field. 

Sabato, however, said early polls are usually never accurate and doubts that Romney could have picked up support. 

He explained that Romney and his supporters never had a good answer to the question of "what would be different this time?"

Without Romney in the field, Jeb Bush came out as the frontrunner in the latest Fox News poll, but not by much. 

Sabato said Romney's decision is good news for Bush, but called this Republican race "one of the most wide open in modern American history."

And he said it's likely to be the largest field of candidates for any modern presidential race.

Sabato said right now he would not call Jeb Bush a "frontrunner," saying he'll face a challenge among so-called "establishment" Republicans from Chris Christie. 

He named Scott Walker, Mike Huckabee and Marco Rubio as potential candidates who could rise into the top tier without Romney in the race.

Watch his full analysis above.