Mitt Romney has clinched the Republican presidential nomination with a win in the Texas primary.

An Associated Press delegate count showed Mr Romney had passed the 1,144 delegates needed to win the nomination during the primary. Early returns show Mr Romney posting a big win in Texas.

It's a triumph of endurance for a candidate who came up short four years ago and had to fight hard this year as voters flirted with a carousel of Republican rivals.

Mr Romney reached the nomination milestone with a steady message of concern about the US economy, a campaign organisation that dwarfed those of his Republican opponents, and a fundraising operation second only to that of his Democratic opponent in the general election, president Barack Obama.

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