The Mason-Dixon survey showed that 51 percent of likely voters favored Bush, against 43 percent who said they would vote for Kerry, the Sun Sentinel daily said. Other polls conducted a month ago showed the two running neck-and-neck, or Kerry taking a slight lead. Analysts say a month of heavy advertising by Bush in Florida has hurt Kerry’s image on the southeastern state. In November, before Kerry emerged as the presumed Democratic candidate, a Mason-Dixon poll showed Bush holding an advantage of at least 20-percentage points over any rival. In 2000, Bush’s majority of just over 500 votes in Florida enabled him to defeat Democrat Al Gore and win the presidential election.