Rand Paul’s latest ad in the Kentucky GOP Senate primary touts the support of former Alaska Gov. Sarah Palin, who is bucking the GOP establishment to weigh in on his behalf.Paul first received Palin’s endorsement in February over Secretary of State Trey Grayson, who is viewed as the choice of national Republicans in the race to succeed retiring GOP Sen. Jim Bunning. But Paul, a tea party movement favorite, has led Grayson in recent public polls and even picked up the surprise endorsement of Bunning last week.The 30-second television spot, which began airing in the state’s major media markets Monday,...