Read the full Pew Research Center poll

Barack Obama has built a “broad-based advantage” over Hillary Clinton among Democrats nationally, and also leads John McCain in a general election match-up in a new Pew Research Center survey conducted Feb. 20-24. But the poll also found that Obama faces some important challenges ahead.

Obama leads Clinton among Democratic primary voters by 49 percent to 40 percent and 70 percent of those believe he is most likely to win the party’s nomination. The margin of error for this sample is 5.5 percent. Both Obama and Clinton both lead McCain in a general election match-up, although Obama leads by a slightly larger margin, 50 percent to 43 percent compared to Clinton’s 50 to 45 percent. The margin of error for all voters is 3 percent.

Obama’s lead over Clinton reflects the fact that support for Clinton has “slipped all across the board,” Pew says. The only groups in which she now leads are white women voters, voters over the age of 65 and voters with household incomes of less than $30,000 a year.