WASHINGTON (Reuters) - President Bush's lead over Democratic nominee John Kerry narrowed to eight points in a CNN/USA Today/Gallup poll of likely voters released on Monday, compared with a 13-point lead in the poll conducted two weeks ago. The survey of likely voters showed 52 percent would vote for Bush and 44 percent for Kerry. A similar poll conducted from Sept. 13-15 showed Bush with 55 percent compared to Kerry at 42 percent. However, among registered voters Bush's lead widened to 13 percent with 54 percent supporting the president and 41 percent backing Kerry. It was up from the earlier...