Dan Balz and Philip Rucker write for The Washington Post:
Mitt Romney captured presidential primaries in Maryland, the District and battleground Wisconsin, the biggest prize of the day, to complete a momentum-building, three-contest sweep Tuesday that cemented his status as the almost certain Republican nominee and put new pressure on rival Rick Santorum to reassess his candidacy.
With his campaign increasingly focused on President Obama and the general election, the former Massachusetts governor’s victories in Maryland and the District were never in doubt. He won both by crushing margins. In Wisconsin, where Romney and Santorum devoted most of their energies, the margin was narrower but nonetheless decisive.
With Tuesday’s primaries behind them, the candidates now look ahead to April 24, when Pennsylvania and four other states hold their primaries. Santorum, a former senator from Pennsylvania, can ill-afford to lose his home state and has keyed the future of his campaign to success there, a reality openly acknowledged by his advisers.
The urgency for Romney to pivot away from intraparty warfare toward the general election contest became even more apparent on Tuesday. On a day he formally clinched the Democratic nomination, Obama delivered a speech clearly designed to frame the fall choice. He sharply attacked the budget approved by House Republicans, calling it a “radical vision” and “thinly veiled Social Darwinism” that amounted to “a prescription for decline” in the country.
On Tuesday night, Romney fired back, calling the president out of touch with the suffering in society and saying that on Obama’s watch America isn’t working.
“This campaign is going to deal with many complicated issues but there is a basic choice we’re going to face,” he said in his victory speech in Milwaukee. “The president has pledged to transform America and he has spent the last four years building a government-centered society. I will spend the next four years rebuilding the foundation of an opportunity society led by free people and free enterprise.”
Already there is a rising chorus of party leaders urging that Republicans rally around Romney, while carefully avoiding direct calls for Santorum to get out. Party leaders fear that an extended contest that includes a continuation of the negative attacks that have been pervasive throughout the primaries will only weaken the party and its likely nominee for the fall.
Santorum runs the risk of either embarrassment, if he loses Pennsylvania, or becoming seen within his party as a spoiler if he stays in the race indefinitely and continues to attack Romney.
But on Tuesday night, he sounded a defiant note in his concession speech.
Saying the race was only at its halfway point, he vowed to keep campaigning and threatened to take his candidacy all the way to the GOP convention in Tampa. He laced his remarks, delivered in Pennsylvania, with criticisms of Romney, calling his rival a moderate who lacks true convictions.
“If we’re going to win this race we can’t have little differences between our nominee and President Obama,” he said. “We have to have clear contrasting colors.” He said people have gotten behind his candidacy “because they see someone who has a clear positive vision, someone whose convictions are also forged in steel, not on an Etch A Sketch.”