Do open primaries favour plutocrats and extremists? – Telegraph Blogs
Open primaries allow for tactical voting schemes which are a barely legal form of vandalism. If the Democrats have a left of center candidate running with only token opposition in the primary but vulnerable to a likely Republican in the general election then they can urge their extremist and fringe supporters to vote in the Republican primary for a vulnerable fringe candidate. The Republican primary is usually decided by a small number of votes and is more likely to be subject to this mischief. That may be how the Nazi David Duke got on the ballot in the 1991 Louisiana Governor's race. In fact the Democrats benefit additionally by having their potentially disruptive fringe members vote in the Republican primary.
The English model of strong local constituency organizations that have standing members who approve the candidates is a surer protection. Obviously steps must be taken to preserve the independence of the local party groups from domination by central organizations with their own agendas.
(reply to alhamilton)
Running them all at the same time, as in a National Primary, does nothing except add problems from the time zone effect where West Coast voters are influenced by East Coast returns. Tactical voting does not necessarily weaken the Democrat in the primary for the reasons I have given. It reduces the influence of extremist voters in the Democratic Primary which strengthens the Democrats for the General election. It allows a small cadre of activists to derail the Republicans due to the small number of voters in many Republican primaries. I would prefer that local parties who choose candidates or State Committee members who then choose candidates be run like private corporations or non-profit social clubs, with provision to ensure that members who freely join and support the organization get to choose the leadership and select the candidates. The only people who benefit from the primary system are the advertisers and media corporations who make money off the current system. Allowing people who are not even previously affiliated with the party to vote in a Primary compounds that problem.
The worst system is the open caucus that invites fraud by having a rent a crowd show up to pack the room. That was what David Axelrod engineered to get Obama the nomination after Hillary Clinton won the Primaries and then lost the same day caucuses in Texas and Iowa.