Hamilton on the Guarantee Clause

In a Findlaw column on Lopez Torres, Marci Hamilton revisits California Democratic Party v. Jones, in which the Court strikes down, on First Amendment grounds, California's Prop 193, which had tried to force parties to have open primaries.  She thinks this was an unnecessary intrusion into state sovereignty -- but hints that there were alternative grounds to get rid of Prop 193's effect.  The one based in the Guarantee Clause interested me especially:

How Prop. 198 Also May Have Violated the Constitution's Guarantee Clause

If the Court was intent on striking down Prop.198, moreover, there was a much more sensible way to do so: Invoke the long-mothballed Guarantee Clause.

The California initiative system permits individual voters to secretly cast ballots for important public policies, without ever having to account publicly for their views. It is a convenient alternative for legislators shirking difficult issues, and it lets voters follow their less respectable instincts in the privacy of the voting booth.

This system is disturbing to begin with, and even more so if the issue is how to create a fair system of elections. In this area, especially, the Court could have held that only elected representatives -- who must be publicly accountable to the people and articulate their reasons for their choices -- may make such decisions. Such a decision would have introduced public accountability into a system that historically has been capable of building some ugly barriers grounded in racism and sexism. The problem, however, is that the Court has refused to enforce the Guarantee Clause, partly to defer to state processes. It is the height of irony that it would eschew the Guarantee Clause's direct application to governing structures in favor of a theory of the First Amendment that addresses election processes.

Of course, I'm much more sympathetic to direct democracy so don't have quite the same starting point as Hamilton.  But I'd also have thought that the argument for direct democracy is strongest on matters of electoral reform, where we can most expect legislators to act in their collective and individual self-interest.  Here, since parties control the fate of virtually all legislators, it is odd to argue that direct democracy is especially inappropriate in the context of party regulation.  "Accountability" issues aside, isn't there a much more substantial self-dealing worry we have about letting legislators control electoral reform?