WASHINGTON (AP) - Mitt Romney has added a win in Delaware's Republican presidential primary to GOP victories in Connecticut and Rhode Island.

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The three are among a string of five state primaries being held Tuesday. The others are in New York and Pennsylvania.

The five primaries are the first since Rick Santorum suspended his presidential campaign two weeks ago and essentially conceded the GOP nomination to Romney.

Romney started the day with 698 delegates -- about 400 short of the number he needs to formally gain the nomination this summer at the Republican National Convention. There are 209 delegates at stake in Tuesday's five primaries.

Newt Gingrich had campaigned heavily in Delaware, hoping for a win there.