Are the DUP playing a dangerous game?

Mick Fealty over at Brassneck has cast his eye over the DUP no-show at the crucial Westminster vote on the setting up of an investigatory committee into the arrest of Damien Green. Ming Campbell's amendment was only defeated by 4 votes. From Mick's article:

But there was one whole party missing from the fray. The Democratic Unionist Party have 9 MPs who failed to show on Monday. That's no surprise since they all double job at the Northern Ireland Assembly; which only sits in plenary on Mondays and Tuesdays.

It's angered some of the local Tories. Jeff Peel said:

“It makes a total mockery of the DUP’s claims to be committed to the Union when the Party’s entire cohort of 9 MPs can’t be bothered to turn up or are otherwise engaged. At times when it’s critical that they play their part in democracy they singularly fail to deliver.”

And yet there is another way of reading this. Cameron's choice of Ulster Unionists with their one MP against a looser understanding with larger DUP, means there is no back channel to help them scramble the necessary numbers on a tight vote like this.

With reports today coming through of David Cameron's Conservatives down to a 4 point lead in the polls, the possibility of a hung parliament looks more likely than ever. There has been rumours that an election may be called for June to be held on the same day as the European election. Could the DUP be demonstrating to the Tories the consequences of their deal with the UUP ie don't assume that you will have our support in the future?