Why haven't any states gone the unicameral, parliamentary route?

[politicallefty]

I don't think it's too surprising that bicameralism is commonplace among the states. Unicameralism is really the exception among modern democracies, though somewhat more common among subnational entities. In any event, unicameral legislatures as a whole have been a more recent development. Currently, all upper houses just represent larger districts than their lower house counterpart. Pryor to Reynolds v. Sims in 1964, representation in state legislatures was not subject to the "one man, one vote" principle. Many states had upper houses that represented counties (the California Senate was one such body). If anything, I think bicameralism in most states is just a holdover from the relatively recent past.

As for why states haven't adopted parliamentary systems, I have no idea. It's puzzling to me, as I think many states (especially those that are under one-party rule already) would function far better that way. For example, I think California would function far better under a parliamentary system. Separation of powers is vastly overrated at the state level. Some states have very weak governors, including some that require only a simple majority of the legislature to override a veto. That's not to mention when states like Massachusetts or Wyoming elect governors opposite their typical partisan leanings. That only gives the facade of checks and balances. Ultimately, it's the lopsided supermajority legislatures that are running things.

I would really like to see some states adopt parliamentary systems (let alone the US as a whole). I think it's a far superior system that provides for both accountability and transparency. Ultimately, the party in power holds full responsibility for the actions during its tenure. A parliamentary majority holds total responsibility for its actions and the opposition party is firmly established and ready to govern should the majority fail. The failure of the current system is that when one party is in power, the opposition is disordered and in disarray and always opposes. A parliamentary opposition has a face and can provide constructive opposition. As for divided government in our current system, both sides will essentially point the finger at the other side, which reduces accountability. Keep in mind that the crux of the parliamentary system is that the executive is ultimately accountable to the legislature. The executive must hold and maintain a majority in the legislature to keep power.

And, to add to the debate on republicanism, parliamentary republics exist in many countries. I'd note Israel as a unicameral and Italy as a bicameral parliamentary republic. Besides, the Supreme Court has already ruled that that clause is a political question beyond the purview of the Court. Any state would be free to adopt a parliamentary system. Many parliamentary systems also maintain single-member districts with first-past-the-post, not to mention that fixed terms could easily be set in stone as well (with the exception of non-confidence votes). The two-party system could easily survive in a parliamentary system. However, if the two-party system fell apart and more parties appeared, I fail to see how that would be a bad thing.

[politicallefty]

Would you support having a Senate and a weak head of state? In Australia we have a single transferable vote and proportional representation system for Senate elections that allows third party and independent candidates to be more competitive. Often, third parties can hold more power as a minority swing vote on the cross-bench in the Senate than they otherwise would as part of the Government or Opposition.

Even I'd be nervous about concentrating the entire federal government into a unicameral legislature. I'd leave the Senate as it is and make the Head of State basically entirely ceremonial.

See my proposal in the "28th Amendment" topic:

Section 1. The executive Power shall be transferred from the President and vested in a Prime Minister of the United States, who shall be chosen by a majority vote of the whole membership of the House of Representatives upon its convention. The Prime Minister shall first choose a Cabinet, which shall be established by Law and subject to confirmation by the House of Representatives.

Section 2. The House of Representatives shall be composed of Members chosen every fourth Year by the People of the several States, except upon a majority of Representatives having voted to declare non-confidence in the Prime Minister and Cabinet. If the House of Representatives has voted to declare non-confidence, the House of Representatives shall be dissolved and the Prime Minister shall order Writs of Election for all Representatives to occur no sooner than thirty days and no later than sixty days upon such declaration. The House of Representatives shall convene for its Term no later than thirty days upon its Election.

Section 3. The Times, Places and Manner of holding Elections for Representatives shall be prescribed by Congress.

Section 4. Every Bill which shall have passed the House of Representatives and the Senate shall become Law.

Section 5. This amendment shall take effect upon the next Election of the House of Representatives occurring no sooner than ninety days after the date of ratification.