Chris Mason: What to expect from Thursday's double by-election

There are two seats being contested - Tamworth in Staffordshire and Mid Bedfordshire - on Thursday.

And there are two things that matter: the psychological and the psephological.

They shape the psychology of the parties - how they see themselves and how they perceive voters see them.

But don't forget the psephology as well. That is a posh word for the numbers in elections.

But with Labour a long way ahead in national opinion polls, when the party fails to win in a spot where it has thrown plenty at winning, the awkward questions follow for them.

Both these contests are competitive.

In Mid Bedfordshire, it is a three-way scrap between the Conservatives, Labour and the Liberal Democrats.

In Tamworth it is a straightforward tussle between the Conservatives and Labour.

As ever, all sides indulge in expectation management beforehand.

A gentle or sometimes brutal talking down of their chances, in the hope, from their perspective, of surprising on the upside when the results come in.

It is true the Tories did do badly. But they won one of the three by-elections.

Once again, the Conservatives are sounding gloomy.

"Grumpy Tories can't be bothered," said one Tory figure.

"Our base is not hugely motivated. They are by-elections. You are electing someone for a year or less.

"It's not a great call to action to turn out is it? And both have come about because of the psychodrama of the last year or so at Westminster."

The Conservatives are expecting a huge slump in their share of the vote.

But plenty in all the camps say that while plenty of Conservative voters last time have lost faith in the party, they are not necessarily enamoured by Labour.

There is then the issue of what nerdy political types call "differential turnout".

In other words, which party is best at getting its usual core supporters to vote.

In by-election contests, where turnout often slumps, this could prove crucial.

In Mid Bedfordshire, Labour have had a spring in their step for quite a while.

"It was mid-summer when I started here, and now there are folk putting up their Christmas decorations," says one Labour figure, adding it has been "the longest by-election campaign in history".

The campaign began when the former Conservative MP Nadine Dorries said she would resign.

But it took her rather a while to actually getting around to doing so.

The twist in Mid Bedfordshire is not only are the Conservatives, Labour and the Liberal Democrats all throwing quite a bit at it. It is, to quote one campaigner "like walking in fresh snow".

The patch has been Conservative for so long, none of the parties began with very much precise data about previous voting patterns, beyond the obvious - which is most voters voted Conservative last time out.

Labour folk point at the psephology - the numbers - and describe winning as "a moonshot".

But others within the party say "moonshots do happen".

What may prove crucial is how split the anti-Conservative vote is between Labour and the Liberal Democrats, and how many Tory voters the Conservatives can persuade to turn out.

The Liberal Democrats knocked on 3,500 doors in the constituency over the weekend and appear to be turning their attention to the dozens of villages where former Conservative voters might be persuaded to back Sir Ed Davey's party.

The Conservatives reckon the antics of their previous MP, Ms Dorries, will hurt them.

"It's bad enough when an MP packs it in to take a seat in the House of Lords. She has packed it in because she didn't get a seat in the House of Lords!" says one party hand.

"Of course No 10 are planning to blame me," responded Ms Dorries.

In Staffordshire, the Tamworth tussle is fascinating.

There is rich political history there. In 1996, a year before Labour's landslide, they won a by-election in South East Staffordshire, which included Tamworth.

You can watch the BBC's election programme from the night here.

The MP, Brian Jenkins, held the seat until 2010.

The two seats are not identical, but Labour did hold it while it was in government, and the Conservatives have held the Tamworth seat for as long as they've been in government.

And held it with a colossal majority in 2019.

Labour sources have been sounding consistently less positive about their campaign in Tamworth than the one in Mid Bedfordshire and also label winning it as "a moonshot".

Both Conservative and Labour people express a frustration at the bandwidth, energy and money these by-elections all suck up.

The party machines are thinking of the general election.

But by-elections keep coming - with MPs already anticipating the possibility of a few more, in Wellingborough and Blackpool South.

As for Tamworth and Mid Bedfordshire, keep an eye out for the psychology - how the parties react to who wins and who loses.

And the psephology, the numbers - the change in support for the parties whoever ends up winning.

Both do matter. As do who actually wins.

The Conservatives could do very badly in both and still win. But them losing one, or indeed both, could happen too.