An initiative is currently circulating in Massachusetts for a top-two system. On June 22, the Massachusetts Supreme Court refused to block the initiative from the ballot. Jackson v Attorney General, SJC-13904. Here is the Opinion.

The opinion implies that if the initiative banned write-ins in the general election, it would be unconstitutional. The Court cited its own 1895 decision that said write-ins can never be prohibited. The Court also hinted that if the congressional/state office primary were much earlier in the year, the initiative might be unconstitutional. It quoted from the Ninth Circuit decision that said the Washington state top-two system is constitutional because the primary was in late August, close to the peak of interest in the election. It also quoted the part of that decision that said it would be different if the primary were as early as March.