Judging the Liberal Democrat result in the Richmond Park by-election will be much simpler than it was for Witney as in this case it’s very simple. A good result, and a realistic result, is for Sarah Olney to win.

But there is a little more to judging the result when it arrives in the early of Friday morning than just that simplicity.

First: what happens to the Labour vote?

If the Liberal Democrats have regained the ability to squeeze Labour heavily in Conservative-Liberal Democrat contests, that is another important step on the road to Lib Dem recovery as such tactical voting (enhanced by bar charts, of course) is important to winning under first past the post.

It will also be of wider political significance too, because it will show that voters are more willing to self-organise into an anti-Conservative coalition, without needing any formal party deals, pacts or memorandums.

Such voter-led realignment has been the most effective form of realignment previously. Moreover, a big reduction in such tactical voting saw the Labour vote go up, helping the Conservatives win, in a string of formerly Liberal Democrat constituencies in the 2015 general election.

Second, how high does the Liberal Democrat vote share go?

It is likely that votes for Labour and minor party candidates will be so heavily squeezed that even if the Liberal Democrats get to just above the party’s winning share on gaining the seat in 1997 (44.7%) it may not be quite enough to win this time round. Remember too that the Liberal Democrats started off on under 20%, with just 19.3% in the 2015 general election. So a massive and, in terms of the party’s prospects, very promising vote increase which is still frustratingly short of victory is certainly possible.

Third, what happens to turnout?

Turnout always drops heavily in Parliamentary by-elections, so ignore the usual froth about turnout being down on the general election. That’s about a popular, but useless, piece of political commentary. What matters is how it compares to other similar by-elections.

Witney has a 73% turnout in the 2015 general election and a 47% by-election turnout. Richmond Park scored a 77% turnout last year, so take 51% as a rough yardstick of whether to think of the turnout this time as being on the high or low side.

Lower turnout may well indicate Conservative Remain voters reconciling the different political pressures on them by not voting. That would match up with the stories of Liberal Democrat canvassers being told by Conservatives how cross they are… that they are going to have to vote Lib Dem. Others in a similar position deciding to sit out the contest would be a bad sign for the Conservatives in future rounds of elections of all sorts.

Of course, at it’s simplest, the more votes the Liberal Democrats get, the better for the party, so here is the information on how to help in the last few days.