Romney turns on Obama
Washington - Republican Mitt Romney trained his sights on President Barack Obama on Wednesday after a triple primary win that put him in a commanding position to take the party's presidential nomination.
Romney thumped main rival Rick Santorum in Maryland and the US capital Washington on Tuesday, and won a tighter but more important race in Wisconsin, US media projected, in a pivotal night for the party's frontrunner.
"We won them all! This really has been quite a night," Romney told supporters in Wisconsin, where he won by nearly five percentage points.
Vowing to fight on, Santorum travelled to his home state of Pennsylvania to campaign for the next Republican primary later this month.
Romney has 652 delegates after Tuesday's primaries, well over half the 1 144 needed to be crowned the Republican flag-bearer at the party's national convention in Tampa, Florida in August.
With that momentum, Romney has sought to turn his full attention to Obama and the November presidential elections.
Romney is already acting like the nominee, training his political fire on Obama's "government-centred society" and no longer mentioning his Republican rivals on the campaign trail.
Obama also has moved into campaign mode, rebuking Romney by name in a speech on Tuesday, calling him to account for supporting a "radical" budget passed by congressional conservatives last week and accusing him of "social Darwinism."
Romney fired back on the radio show of conservative host Sean Hannity.
"There's no question that under this president, this recovery has been the most tepid, the most weak, the most painful since the beginning of our recorded economic history," he said.
Romney won 49% to Santorum's 29% in Maryland and dominated with 70% in Washington DC, with former House speaker Newt Gingrich and Texas congressman Ron Paul trailing far behind in all three contests.