Mitt Romney wins Wisconsin presidential primary

WAUKESHA -- Mitt Romney won Republican primaries in Wisconsin, Washington, D.C. and Maryland Tuesday, April 3rd, drawing closer to the GOP presidential nomination while rival Rick Santorum's prospects fade. The former Massachusetts governor is heavily favored to clinch the GOP nomination by June.

Santorum has vowed not to abandon his bid despite a string of losses. Newt Gingrich and Ron Paul also remain in the race. Neither is a threat to Romney.

Romney visited Waukesha Tuesday to serve lunch to people at the Cousins Subs store on Pearl Street -- but the event was not without controversy.

Romney and Congressman Paul Ryan -- who has endorsed Romney in the race for president -- handed out free sandwiches to supporters. The state Democratic Party calls that an election violation. "Ryan and Romney and are engaged in something of value in return for an individual voting," Michael Tate with the Democratic Party of Wisconsin said.

Democrats have filed a complaint with the Government Accountability Board (GAB) and the Waukesha County District Attorney.

"A sandwich in exchange for voting. This is a black and white issue. You are not allowed to offer someone more than $1 in exchange for their vote," Tate said.

However, the Romney campaign dismisses the allegations as a distraction.

"Get your friends to go vote, get some friends to vote with you. That's how you can legally vote multiple times. Bring your friends go vote and if you want another sandwich, there are more back there," Romney said.

The Associated Press contributed to this report.