Mitt Romney has taken a
stride closer to the Republican presidential nomination by winning
primaries in Wisconsin, Maryland and Washington DC.He routed his main rival Rick Santorum in Maryland, although his projected margin of victory looked leaner in Wisconsin.Mr Santorum, who has faced calls to bow out of the race in the name of party unity, defiantly vowed to fight on.The eventual winner will face Barack Obama in November's election.
President
Obama attacked Mr Romney earlier on Tuesday in the latest sign that he
views the former Massachusetts governor as his November election
opponent.
Former House Speaker Newt Gingrich and Texas Congressman Ron Paul trailed far behind in the primary results.
In Washington DC, where Mr Santorum was not on the ballot, Mr Romney took 70% of the vote.
Exit polls indicated that Republican voters were primarily concerned with a candidate's ability to defeat Mr Obama.
In
his victory speech on Tuesday, Mr Romney said Mr Obama was an
"out-of-touch liberal" and blamed him for home foreclosures, government
debt and gas prices.
He claimed more Americans had lost their jobs
under the Obama administration than under any other president since the
Depression.
"These last few years have been difficult, made worse by mistakes and failures of leadership," Mr Romney said.
Analysts
say the former Massachusetts governor is close to a tipping point where
Mr Santorum would be unable to catch him in the race.
Mr Santorum only seriously competed in Wisconsin, an agricultural and manufacturing state that was the night's biggest prize.
Wisconsin provided his best result of the night giving him 37.7% of the vote compared to Mr Romney's 42.5%.
In
his speech on Tuesday night, the former senator pledged to fight on to
the primary in his home state of Pennsylvania on 24 April.
He
told cheering supporters: "We have now reached the point where it's
half time - half the delegates in this process have been selected.
Who's ready to charge out of the locker room in Pennsylvania for a
strong second half?"
Longshot candidate Mr Gingrich, a
former House of Representatives Speaker, also vowed on Tuesday to
continue in the race - all the way to the Republican convention in
August.
Mr Romney and his allies have spent an
estimated $53m (£33m) on television advertising so far this election
cycle, compared with $27m from his three Republican competitors
combined.
Mr Obama took aim at the Republican front-runner on Tuesday in a
stinging critique of the budget proposal recently laid out by a
high-profile Romney ally, Wisconsin congressman Paul Ryan.
Addressing
news executives in Washington DC, President Obama said the so-called
Ryan budget was "thinly veiled social Darwinism".
He
condemned Mr Romney for backing the budget, saying: "He even called it
marvellous, which is a word you don't often hear when it comes to
describing a budget.