WASHINGTON (Reuters) - Democrat Barack Obama holds a 4-point lead over Republican rival John McCain in a tight race for the White House, according to a Reuters/C-SPAN/Zogby poll released on Saturday.

Obama leads McCain 48 percent to 44 percent among likely U.S. voters in the latest four-day tracking poll, down slightly from Obama's 5-point advantage on Friday. The poll has a margin of error of 2.9 percentage points.

(Reporting by John Whitesides; Editing by Peter Cooney)