Mitt Romney has won the Republican presidential primary in Texas and the remaining delegates needed to secure the party's nomination for the presidential election.
He will challenge Barack Obama for the White House in November.
With 1086 delegates secured as he entered the Texas race, Mr Romney only needed 58 to pass the 1144 mark needed for the nomination, the BBC reports.
In a statement, Mr Romney, 65, said he was honoured and humbled by the win on Tuesday. He has been the presumed nominee for several weeks as his rivals withdrew or suspended their campaigning.
Mr Romney is the first Mormon from a major party to contest the presidential election and is set to be officially anointed as the Republican nominee at the party convention in Tampa, Florida, in late August.
His father George Romney, a former Michigan governor, unsuccessfully sought the Republican nomination in 1968.
Latest polls suggest that the election will be close and could depend on what happens in a handful of battleground states, including Colorado and Nevada.