Democrat Barack Obama heads to the finish line in the 2008 campaign with an 8-point advantage over Republican John McCain, according to a Wall Street Journal/NBC News public opinion poll released on Sunday. The poll, found 51 percent of likely voters favored Obama , versus 43 who favored McCain. Obama 's lead slipped 2 points from a Wall Street Journal/NBC News poll released last week. The new poll, conducted Saturday and Sunday, has a margin of error of plus or minus 3.1 percentage points.