Does anyone really believe that those determined to muck around in their opponent’s primary will be stopped by a silly signature? In an email exchange Friday, political pundit Larry Sabato told me that the so-called “loyalty oath has been a controversy in both parties for about a century. Of late the Republicans are much more interested in having one than the Democrats. Mainly, the conservative Republicans want to control the party’s nominating process.” The University of Virginia professor dismissed the belief that crossover voting is common.