Should voting in elections be mandatory?

Mandatory voting would increase democratic legitimacy

Question: Should voting in elections be mandatory?
Position1 of 2›: Voting should be mandatory
Argument1 of 3›: Mandatory voting would increase democratic legitimacy

The government is often not overseen by someone with a majority of votes, making it democratically illegitimate.

The argument

The argument begins from a fact about UK election outcomes: no political party since 1931 has won over half of the electorate's support in a general election under the First Past the Post system. Governments are formed, and hold a full mandate to legislate, on the backing of a minority of those entitled to vote. The gap between the authority exercised and the support demonstrated is the problem this argument identifies at the heart of the system. Two things produce that gap. First Past the Post converts a plurality of votes into a majority of seats, so a party can govern alone on well under half the votes cast. Voluntary turnout widens the gap further, because the share of the electorate a winning party commands is smaller still once those who did not vote are counted. It is the second factor that mandatory voting addresses directly. If voting were compulsory, participation would rise towards the whole electorate, and with a far larger share of eligible citizens expressing a preference it becomes likely that one party or candidate would assemble the support of an actual majority of the electorate rather than a plurality of a self-selected subset. The winner's claim to speak for the country would then rest on a demonstrated majority rather than on an arithmetic artefact of who chose to turn out. That is what makes this a legitimacy argument rather than simply a turnout argument. The case is not that more participation is good in itself, but that a government's right to bind those it governs is stronger the more of them have actually been counted. Compulsory voting would close the distance between the electorate as a whole and the portion of it that decides, and in doing so would address a deficit of democratic legitimacy that has persisted in the UK for the better part of a century.

Premises

[P1]A government's democratic legitimacy depends on securing the support of a majority of the electorate. [P2] Since 1931, no UK party has won over half the electorate's support, revealing a legitimacy deficit under current voluntary turnout. [P3] Mandatory voting would raise participation enough to make majority electoral support achievable. [C] Therefore, voting should be mandatory in order to restore democratic legitimacy.

Counter-arguments

There are other ways to increase democratic legitimacy in the UK political system that would not require forcing people to vote, including introducing a proportional electoral system, devolving power to the nations and regions, and allowing the electorate a greater say in selecting the candidates for prime minister.

Rejecting the premises

[Rejecting P3] There are more effective ways to increase democratic legitimacy.