Contests between those of the same party are in their nature divisive and distract from the aim of winning the general election. Debates about Ideological nuance are not major reasons for non-political voters to go to the polls. Debates about those issues have largely been the preserve of those who are party members and as a result should stay within that sphere.  Greater competition can be engendered through other means, such as Proportional Representation that leads to real competition between all parties in all areas of a country as opposed to a contest between candidates who have no real differences of opinion.