Mitt Romney emerged from the Republican primary's biggest single-day contest with the most delegates, but perhaps not the momentum he would have liked.
With seven of the day's 11 states likely in his pocket, Romney increased his delegate lead over closest rival Rick Santorum and approached the halfway mark to the 1,144 needed to elect a nominee at the party's August convention.
But a neck-and-neck race with Santorum in Ohio, considered a national bellwether, meant that Romney could not make the argument that he had effectively sealed the primary race, and was the only man capable of beating Obama.
Al Jazeera's Alan Fisher reports from Boston.
