McCain spoke before supporters in Alexandria, Va.
Sixty-five percent of voters in Virginia's Republican primary called themselves conservatives. Mike Huckabee won half of their votes, including two-thirds of those who called themselves "very conservative." In Maryland, conservatives were a similar share of the voters but McCain actually did better than Huckabee among them. Ron Paul and Mitt Romney, who has suspended his campaign, each got about one in 10 conservatives in Maryland.
Republicans John McCain and Mike Huckabee had struggled over 116 delegates in the GOP primaries in the so-called Potomac Primary contests.
McCain won the votes of 70 percent of moderates in Virginia, almost eight in 10 in Maryland. McCain won about half of those who called themselves "somewhat conservative" in both states.
Forty-nine percent of Republican voters in Virginia said McCain's policies were not conservative enough, slightly fewer said that in Maryland.
The surveys were conducted by Edison Media Research and Mitofsky International for The Associated Press and the television networks. There was no survey conducted in the District of Columbia.
It takes 1,191 delegates to clinch the Republican nomination, and McCain appears to be on track to reach the target by late April.
An Associated Press-Ipsos poll found Obama with a narrow lead over the Arizona senator in a potential match-up, and Clinton running about even.