This Argument does not stack up. The large numbers of people voting in Primary elections will mean many ‘apoliticals’ will counter the worst partisan tactics (if any) being used in the election. If there has been any impact of opposition party involvement upon the internal politics of a party, it has been to elect more centrist candidates that the greatest number of voters can find palatable. That in itself is no bad thing, as politics can become extremely partisan at times, it does help to have candidates who can be moderate and be more prepared to compromise in order to the best possible outcome for all they represent.