TRENTON, New Jersey (Reuters) - New Jersey Governor Chris Christie will announce on Tuesday that he will not run for president in 2012, ending weeks of feverish speculation that he might shake up a wide-open Republican race with a dramatic late entrance.

Christie's decision, Republican sources said, was to be unveiled at a news conference in the New Jersey state capital of Trenton at 1 p.m. (1700 GMT). The move followed days of meetings with advisers on whether he could swiftly put together an organization and mount a credible campaign.

Christie's move will likely benefit former Massachusetts Governor Mitt Romney because they would have been competing for the same middle-of-the-road voters. Romney leads the Republican field by a large margin in the state that holds the first Republican primary, New Hampshire, which might have been a factor into Christie's deliberations.

The tough-talking Christie, 49, would have immediately energized a field that lacks firepower and which many party faithful are unenthusiastic about.

Romney, Rick Perry and Herman Cain are jockeying in the top three positions in the field, and many Republicans have been clamoring for a fresh face and wanting the strongest candidate possible to run against Democratic President Barack Obama in November 2012.

While not impossible, it would have been a difficult challenge for Christie to raise money, enlist activists and build a nationwide team in time for the start of the nominating process, which is to kick off in early January with the Iowa caucuses followed shortly by the New Hampshire primary.

The only potential candidate left who could make a major impact on the race is former Alaska Governor Sarah Palin, who has said she is still considering it. She has left doubt, however, by saying last week that having the title of president might "shackle" her.

Christie has stated over and over that he is simply not ready to be president after only two years as governor, and would have been forced to explain why he felt compelled to change his mind.

He may have also had trouble connecting in Iowa, where the rock-solid conservative views of Texas Governor Perry and Minnesota Congresswoman Michele Bachmann are more welcome. Christie has fairly moderate positions on immigration and climate change that are out of step with conservative orthodoxy.

Many activists had wanted Christie to run because he is an electrifying presence and has a strong fiscal record in New Jersey.

(Reporting by Kim Dixon, Steve Holland and Mark Egan, editing by Philip Barbara)

Source: Reuters US Online Report Politics News