WASHINGTON: Mitt Romney clinched the Republican presidential nomination on Tuesday with a win in the Texas primary, a triumph of endurance for a candidate who fought hard to win over skeptical conservative voters he must now fire up for the campaign against President Barack Obama.

According to the Associated Press count, Romney surpassed the 1,144 delegates needed to win the nomination by winning at least 88 delegates in the Texas primary.

Romney, who came up short in the Republican presidential race four years ago, outlasted a carousel of Republican rivals who dropped out of the State-by-State primary contest. None of his former rivals actively campaigned in Texas.

The former Massachusetts Governor has reached the nomination milestone with a steady message of concern about the U.S. economy, a campaign organisation that dwarfed those of his Republican foes and a fundraising operation second only to that of Obama, his Democratic opponent in the general election.

Romney must now energise conservatives who still doubt him, while persuading undecided voters that he can do a better job fixing the nation’s struggling economy than Obama.

“I am honoured that Americans across the country have given their support to my candidacy and I am humbled to have won enough delegates to become the Republican Party’s 2012 presidential nominee,” Romney said in a statement.

“Our party has come together with the goal of putting the failures of the last three and a half years behind us,” Romney said. “I have no illusions about the difficulties of the task before us. But whatever challenges lie ahead, we will settle for nothing less than getting America back on the path to full employment and prosperity.”

In Obama, he will face a well-funded candidate with a proven campaign team in an election that will be heavily influenced by the economy.