CNN projected the former Massachusetts governor was an easy winner in Indiana, where 46 delegates were at stake, with only U.S. Rep. Ron Paul of Texas still in the race.
With 99 percent of precincts reporting, CNN said Romney had 64 percent (340,594 votes) to 15 percent (80,617) for Paul and 14 percent (72,794) for former U.S. Sen. Rick Santorum of Pennsylvania, who pulled out of the race last month.
Romney went into the day's primaries in Indiana, North Carolina and West Virginia with 865 of the 1,144 delegates needed for the GOP nomination. Paul had 93. Romney won in North Carolina Tuesday.