WASHINGTON (AP) – Barack Obama has developed a clear lead nationally over Hillary Rodham Clinton – 54 percent to 41 percent in the Democratic presidential race, a Pew Research Center poll shows.

That’s a change from April, when the same poll found he and Clinton were running about even.

Three in 10 Democrats think the party will be divided if Obama wins the nomination, up slightly since March, with Clinton supporters twice as likely as Obama’s to say so, according to the survey.

When matched against Republican John McCain, Obama is now running about even among all voters; he’s had a narrow advantage over McCain most of the year.

The Pew Research Center poll was conducted from May 21-25 and involved telephone interviews with 1,242 registered voters, for whom the margin of sampling error was plus or minus 3.5 percentage points. It included interviews with 618 Democratic and Democratic-leaning voters, with a margin of sampling error of plus or minus 4.5 points.