PR under FPTP

Any Member of Parliament could be elected on the following manifesto:

1. "In Parliament, and in all my work with the public, and before public scrutiny, I will remain a spokesperson for my party. I will show the greatest sympathy to my party line, although I will of course take care to refine it, and to constructively criticize it, whenever my intelligence and my conscience suggest that that is necessary."
2. "However, in any parliamentary vote, I will always vote according to the wishes of the majority of my constituents. Sometimes -- even often -- that may require me to vote against my better judgment. But I will do so, respecting the higher principle that I am my constituents' delegate in Parliament."

In constructing such a covenant for voters, the details are important. In particular, the details of how the MP would seek to know their constituents' wishes. The core mechanism would be secure and accessible online polling. But provision would have to be made for constituents who didn't have reliable internet access, or who couldn't figure out their phones. Some provision could also be made for constituents who were too beaten down, busy and/or jaded to actively involve themselves.

The covenant would also have to set precise thresholds which, if not met, would permit the MP a degree of discretion. At least two kinds of threshold would be involved. Ideally these should be interlinked, although there are also good reasons to avoid making the covenant too complex.

1. A support threshold. The higher the proportion of constituents who support a particular vote, the more binding it should be on the MP. A very evenly split constituency should give the MP (or the MP's Whips' Office) the chance to exercise discretion. (For instance the covenant might include some provision like this: if fewer than 40% support a particular Bill, the MP must vote no, if it is 40%-47%, the MP may choose between no and abstention; if it is 48%-52%, the MP may choose between aye, no, and abstention; if it is 53%-60%, the MP may choose between aye and abstention, and if it above 60% the MP must vote aye).
2. A quorum threshold. If very few constituents are interested in a particular poll, it may provide a skewed result. 

The covenant should also have a legal contractual form, so that constituents would have the option of pressuring a rogue MP through the courts.

At the present moment, the approach I have described might appeal to any single-issue independent candidate without a great chance of winning. It could potentially appeal to Liberal Democrat or even the Green candidates in some of their most hopeless-looking seats, and perhaps to Labour and the Conservatives in Scotland. At first it would have to varnish wonkishness with hope. If the approach were successful in winning a seat, or even in a startling gain for an outlier, it would no doubt be adopted by others at the next election.

As I see it, there are two main kinds of danger.

1. New forms of voter intimidation, treating, and misinformation, new patterns of exclusion and disenfranchisement, and in particular, the rise of canny MPs who learn to filter and manipulate polling to produce whatever mandates they want. What if, after a few successful iterations, an MP "refines" this democratic practice, by introducing a short quiz prior to each vote, just to make sure that only "properly" informed constituents have their voices listened to?
2. The public getting its way.