Election 2012: Primary Day Arrives in D.C., Maryland and Wisconsin

Republican front-runner Mitt Romney and President Barack Obama are trading jabs even before Republicans vote in their latest presidential primaries, a sign that both sides believe the race to decide who will oppose the Democrat this fall is coming to a close.

With GOP primaries Tuesday in Wisconsin, Maryland and the District of Columbia, Romney is set to hold one campaign event before an election night party in Milwaukee. He spent the weekend campaigning across Wisconsin, working to win yet another big industrial state that rival Rick Santorum was counting on to keep his flagging candidacy alive.

"Take the next step here in Wisconsin," Romney urged supporters at his last campaign stop Monday. "I need you to go out and vote. Get your friends."

Obama is treating the former Massachusetts governor as though he's already won the GOP nomination.

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