Csdrhrt

Unfortunately for your idea, the core voting mechanism in Westminster (and the only one which is viewed as acceptable for legislation) requires a yes/no question and a binary vote. Indeed the voting actually occurs by travelling down corridors on either side of the debate lobby. Your options 1 and 4 require such a vote (for option one, a somewhat specific motion needs to pass to ratify the deal, while for option four several votes on the bill to create a second referendum would need to pass).

In principle options 2 or 3 could proceed through plurality if the House chose, since leaving with no deal is the default position if nothing else happens and since extending the date only requires there not to be a majority against such an action (and it's already known that there is majority in favour of requesting an extension).

In fact there have been several proposals to call a series of "indicative", non-binding votes along the lines of what you propose, which could conceivably form a consensus around the most popular option, but that still doesn't mean that an option the majority would vote down has much chance (excepting option 3 which could essentially happen by accident at this point.)

Plurality votes are notoriously open to manipulation. Let's say you are proposing something unpopular, such as a 10% tax increase. Only 40% of MPs support it.

In a plurality vote you can get the measure passed by creating two artificial alternatives - one leave taxes the same, and one to cut taxes by 10%. If half of those opposed to the measure vote each way, then the tax increase has the most votes and will pass.

No legislative assembly I am aware of uses plurality votes, at least partly for this reason.

There is quite simply no mechanism in Parliament for a plurality vote among more than two options to exist. In order to have a plurality vote you would need to first pass a bill change to the Commons standing orders creating that mechanism, and the majority against the best predicted result would most like vote that bill down.

But even that might not work. The very next thing brought to vote might well be a binding vote to specifically cast down the result chosen from the plurality vote, and will have a majority backing that, so down it goes. There may or may not be procedures that would suffice to block this from coming to a vote, but blocking something with a known outcome from reaching the floor doesn't look like a democracy anymore.

There is no reason why these options could not be put to Parliament in series.

The House of Commons works by having the government propose motions that can be passed or rejected. Motions are allocated time to be debated and other MPs can propose amendments. Finally a series of votes on the amendments and finally on the motion (amended or otherwise) are held.

The problem is that on all but one day a year only the government gets to decide which motions are going to be voted on. And the government is mostly controlled by the Prime Minister, and Mrs May only wants one outcome: her deal is accepted.

As such it's extremely difficult to get votes on the other options. The best hope is for amendments to be accepted supporting those options, but even then the Speaker of the House gets to decide which amendments will be put to the vote so it's not always automatically possible to have them attached to a government motion.

So it's entirely possible, just very unlikely due to Theresa May.

So, why not break the deadlock by plurality?

As of now, the British government is no longer in deadlock. There has already been a vote on all of the listed options except for option #5 and only the second option (asking for an extension) managed to receive more than 50% of the votes. Thus Theresa May asked for a three month delay on March 20th, currently pending approval by the European Council. Holding a plurality vote would be redundant as no other option had more than 50% of the MPs support.

In three months time (presuming the EU will grant the UK an extension), Parliament will again have to choose between the options, but this time asking for an extension would no longer be possible.

Let's say the government proposes this and this vote is carried out. Then a majority of MPs are getting something they don't want (otherwise that outcome could be passed as a normal vote by simple majority). In particular, the government may get an outcome it doesn't want, the majority of parliament doesn't want but would have to carry it out (well, that would be part of the earlier proposition of this system, otherwise the vote would be meaningless). This isn't ideal.

Aside from that, those options aren't a one-time thing. These actions have consequences and once you choose an option, you have to follow through:

1. For example, if you accept the current deal, many laws will have to
   be passed (which requires a majority, again).




2. If they decide to keep on negotiating the impasse isn't broken, they
   will just have one more option if a new deal is negotiated, but
   there may be no majority for that one either.




3. Leaving without a deal is like opening Pandora's box, it's not
   something that solves all existing problems, instead many more
   choices (e.g. what will be the policy on allowing EU citizens coming
   to the UK? How are goods coming in checked?) will have to be made
   and that requires a majority in parliament to do so.




4. A second referendum also doesn't help if there is no majority in
   favour of it. In the proposed plurality vote, do MPs commit to
   respecting the outcome? Even if that means disrespecting the current
   referendum outcome? If the outcome is to leave without a deal, what
   instructions does that give the parliament / government with regards
   to the previous point?

All in all, it's not that easy. And if MPs do decide they want to work together to get a certain outcome, they can just do that. They wouldn't need the plurality vote. For example, the leaders over the parties could meet, decide an outcome, whip their MPs and don't care about a few people not voting with their decision. Obviously, the problem is that the parties aren't willing to compromise in such a controlled setting, they're not going to allow a vote (for which they don't really know the outcome) and then magically decide to respect that.