Perhaps eliminate the primary unless more than two candidates are running?
The one problem with that is that the system would be disjoint if that were done but voters could still vote for write-in candidates in races with a primary, and (while they possibly could have; I've heard Hawaii has no write-in candidate option for at least many of its elections, not just runoffs) the Grangers might not have wanted to bar write-in candidates from running, particularly in races where only one candidate was on the primary ballot. Can a write-in candidate in an otherwise one-candidate primary get on the general election ballot if they get enough votes? Is there a minimal number of votes for each office that a write-in candidate needs to get on the general election ballot (provided of course they are among the top two candidates in the primary)? I imagine it isn't simply 1 vote for all offices. If that were the case in Maine the Maine Green Indepdendent Party might actually field candidates in all "top ticket" races (for Governor where they always field a candidate, and for U.S. Senate and Congress where they never have fielded an official party candidate although they tried to for the Senate 1996 when they were an official party but that guy had to run as an Independent because not enough voter enrollments had been successfully done), plus a majority of Legislative races instead of the 10 or 13 respectively of 186 they ran candidates in 2006 and are doing this time. A Republican write-in candidate tried to get on the ballot for state Representative but I've heard he got only 33 write-in votes where 50 were needed, so the Democratic incumbent in that race will be unopposed in November as will 6 other incumbent House Democrats and one Democratic Senator (the former 19-year State House Speaker) who is trading seats with the incumbent State Representative. One incumbent Republican Representative is unopposed, one incumbent Independent Representative (a former Democrat) who seems rather cozy with the Republicans now has only a Democratic opponent, one incumbent Democratic Representative
who replaced a resigned Republican in a special election last November has two Independent opponents but no Republican opponent, and one incumbent Democratic Representative has only a Green Independent opponent.