A survey taken Wednesday through Friday of 1,237 Democratic and Democratic-leaning voters indicates Obama leads rival Clinton 51 percent to 42 percent.

Gallup suggests the lead is in large part due to the media focus on exchanges between Obama and the presumptive Republican nominee and Arizona Sen. John McCain in recent speeches by the candidates.

This drew media attention away from Clinton, which Gallup says implies Obama will get the Democratic nomination. It is suggested in some news accounts, Gallup says, that Obama may "declare victory" after Tuesday's Kentucky and Oregon primaries.

Despite the results for Obama, the same poll of 4,385 registered voters of all parties indicates Clinton has a slight advantage, 47 percent to 45 percent, when pitted against McCain while McCain edges slightly ahead of Obama by a 3 percent margin.

The survey of Democratic and Democratic-leaning voters had a sampling error of 3 percentage points while the general survey quoted a 2 percent margin of error.