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We could have had a month of drama, with our prospective leaders finally brought together to debate. Now it seems unlikely that any TV debate will happen, or that David Cameron will take part if they do – although there are rumours ITV is trying to meet the PM’s demands.

Everything unraveled when the broadcasters invited Plaid Cymru. Now the Northern Irish parties are all quite rightly demanding invitations. If the broadcasters wanted a debate with all the main parties, they should have invited six.

There is a very simple reason why. Six parties are going to win more than a million votes in May: the two you expect plus Ukip, the Greens, Lib Dems and SNP. Do you know who isn’t going to win a million, or come close to? Plaid Cymru.

In 2010 Wales’ nationalists won 165,394 votes. That’s one-seventh as many as the SNP are likely to win in May (presuming they poll nearly 50 per cent, as polls suggest). One-seventh. If only someone had told that to the BBC box-ticker who decided Plaid needed to be included.

Plaid Cymru and Northern Ireland’s parties all won fewer than 200,000 votes in 2010. Clearly inviting Plaid Cymru was going to provoke a challenge from the DUP, who won 3,000 more votes than them in 2010 and have more than twice as many MPs.

You could suggest we’re comparing apples (a prediction for the SNP and others based on polls) to oranges (actual results for Plaid and the Northern Irish from 2010). But the very few Welsh and Northern Irish polls we have suggest that little has changed in either place since 2010. And besides, there just aren’t all that many Welsh and Northern Irish votes to win.

In 2010 Plaid Cymru won one-seventh as many votes as the SNP are likely to win in May.

If you want to turn your gaze to seats, and say Plaid Cymru, who have three seats, should clearly be included if Ukip or the Greens are (who only have three if you add them together), that’s really the fault of the way our elections work.

Small parties should only have a cause for inclusion if their MPs could materially affect who governs Britain after polling day. That is yet another reason why the DUP should be in the debates ahead of Plaid Cymru, if we accept any of them should be.

But we wouldn’t. We’d accept the SNP need to be in the debates – they are going to be Westminster’s third largest party at this rate, and will be able to make or break any government. That’s quite different from holding a handful of MPs.

The point of the debates isn’t to solve every logistical issue and achieve some BBC definition of balance. The point is to make politics interesting and important. David Cameron could never have wavered if the broadcasters had just invited the six main parties the first time round.

P.S. We totted up the population figures and it seems Wales should now only have 31 seats, not 40. So Plaid should really only have 2.3 seats. (And there goes Labour’s other heartland next time we have a boundary review.)