Former Florida governor Jeb Bush launched a White House bid months in the making with a vow to win the Republican presidential nomination on his own merits and stay true to his beliefs - easier said than done in a crowded primary contest, where his conservative credentials will be sharply challenged.

Bush is unquestionably among the top tier in a Republican field of 11 major candidates that lacks a true front-runner.

For Bush, the 2016 Republican contest will test both his vision of conservatism and his ability to distance himself from family.