Factbox: Presidential candidate Mitt Romney

Republican presidential candidate and former Massachusetts Governor Mitt Romney speaks at a campaign rally in Clive, Iowa January 2, 2012.

(Reuters) - Former Massachusetts Governor Mitt Romney will compete in the election year's first Republican presidential nominating contest in Iowa on Tuesday, opening the race for the Republican nomination to challenge President Barack Obama in November.

Here are some facts about him.

* Romney, 64, has remained at the front of the pack among the Republican candidates in his second campaign to win the party's nomination. But he has not been embraced by Republicans as the clear favorite, with one after another of his rivals jumping into the lead for weeks at a time. In Iowa, which has a large conservative Christian electorate that does not support Romney, he has tried to temper expectations but is one of the favorites along with Representative Ron Paul.

* He is a fifth-generation Mormon whose forebears were involved in the religious movement from the mid-19th century. Romney spent 30 months in France as a Mormon missionary in the 1960s, and speaks French. Some Christian groups and voters don't consider Mormonism a form of Christianity.

* In the 2008 campaign, Romney spent millions of dollars campaigning in Iowa only to lose to Mike Huckabee, former governor of Arkansas, and to lose the eventual nomination to John McCain.

* As governor of Massachusetts, Romney instituted statewide healthcare reform that became a model for Obama's national policy. Romney has defended the state law while calling for the repeal of Obama's federal version, a tricky balancing act.

* Romney, a former venture capitalist, has centrist Republican proposals to cut corporate taxes, reduce federal regulations and cut spending. But he is seen by some as out of step with ordinary Americans. During one Republican debate Romney offered to bet $10,000 in a back-and-forth with Texas Governor Rick Perry.

* Multimillionaire Romney has been a strong fundraiser - with more money than any of the other Republican candidates. If the primary contest becomes drawn out, his extensive funds could help him outlast someone like former House of Representatives Speaker Newt Gingrich, who has only raised a fraction of that raised by Romney.

* Animal rights groups criticized Romney during the 2008 campaign for an incident in 1983 when he drove 12 hours to Canada from Boston on vacation with the family dog in a crate strapped to the roof of their car.

(Reporting by Lily Kuo and Deborah Charles; Editing by Eric Beech)