Updated at 9:10 p.m. ET
(CBS News) Republican presidential contender Mitt Romney on Tuesday night came one step closer to securing the GOP nomination with a victory in Maryland, CBS News projects, giving him more than half of the delegates needed to win the nomination.
Romney is expected to win by a decisive margin, according to CBS News exit polling. With polls closed and 74 of 1,892 precincts reporting Romney is winning 53 percent of the vote, while Rick Santorum is carrying 27 percent. Newt Gingrich is carrying 10 percent, while Ron Paul is winning 8 percent.
Romney is also the projected winner in the District of Columbia, according to CBS News, and he is leading in the politically-significant state of Wisconsin.
With his victory in Maryland, Romney has won at least 16 delegates -- 13 awarded for his statewide victory and at least three at the district level -- giving him at least 575 delegates total, according to CBS News estimates. A candidate needs 1,144 delegates to win the GOP nomination outright.
Maryland primary results
CBS News early exit polling: Reservations about Romney dim in Wisconsin
CBS News early exit polling shows Romney winning the support of various voting blocs in Maryland: Fifty percent of men and 54 percent of women back the former Massachusetts governor.
Romney also carries 43 percent of "very conservative" voters -- a group that has in the past favored his main rival Rick Santorum -- while Santorum is winning 37 percent of those voters in Maryland. Romney is also carrying the lead among conservative voters overall with 52 percent support, compared to 30 percent support for Santorum.
Sixty percent of voters who named the economy as the most important issue backed Romney, as did 73 percent of voters who are primarily interested in defeating President Obama in the fall.
Full Republican delegate scorecard
Nationwide primary results so far
CBSNews.com's complete 2012 campaign coverage
Four in 10 Maryland voters say Romney's positions are not conservative enough, but more (about half) say they are about right. A third of voters say Santorum's issue positions are too conservative.
There are a total of 92 delegates at stake Tuesday, with 37 coming from Maryland, 16 coming from Washington and 39 from Wisconsin. The Maryland and D.C. primaries are closed to Republicans while Wisconsin is holding an open primary.
Romney's victory was expected in Maryland, a state that is reliably Democratic in presidential general elections. More focus has fallen on the politically-charged state of Wisconsin.
Before Tuesday night's primaries, Romney had accumulated 559 delegates, according to CBS News estimates, while Santorum had 243, Gingrich had 128, and Paul had 45.
