The Associated Press has projected he has won the Texas GOP primary and will receive at least 58 delegates, giving him the 1,144 needed to win the nomination, according to the current ABC News delegate estimate.
Romney isn't the nominee yet. The 2,286 Republican delegates will officially confer that mantle in August when they select the nominee in a floor vote at the Republican National Convention in Tampa.
His campaign planned no victory party for this long-predicted mathematical triumph. Romney held two public campaign events today, one in Colorado and one in Nevada, and did not mention his imminent clinching of the nomination in either.
The win in Texas brings Romney one step closer to the official conclusion of a long campaign in which he held front-runner or co-frontrunner status from the outset. Romney staved off a revolving cast of Tea Party darlings who included Herman Cain, Michele Bachmann, Rick Perry, Newt Gingrich, Rick Santorum, and for a brief moment, Romney's now-surrogate Donald Trump.
The last major candidate standing against Romney was Ron Paul, the Texas congressman who announced on May 14 that he would no longer campaign in new primary states, but will still organize at state conventions to accrue delegates who will bolster his presence in Tampa, even if many of them will be allocated to Mitt Romney in the presidential-nomination vote.
After Santorum dropped from the race on April 10, Romney became the presumptive winner.
Thanks to a delayed primary calendar and pressure from the Republican National Committee for states to allocate delegates proportionally, this year's Republican primary has dragged on relatively late into the election year. John McCain also clinched the nomination with a win in Texas in 2008, but he did it on March 4.