Could Cameron buy DUP votes with corporation tax?
One big difference between the First and Deputy First Minister is that Martin McGuinness doesn't believe that corporation tax will be devolved here, while Peter Robinson hasn't given up so far.
We may get some indication who is right if their planned meeting with David Cameron is completed today.
Then, the prime minister may give them some indication of whether he has plans to make the change in the lifetime of this parliament.
The decision on whether to do it, or not, won't come until autumn 2014, but has Mr Cameron thought of a way to do it?
If he hasn't planned the logistics, that will be a sign that Mr McGuinness is right and we are going to get a 'No' from him next year.
Why should he do it? For one thing, it could pave the way for the long-term means of reducing our subsidy from Westminster, which, on current estimates, costs the UK more each year than EU membership. And we know what an issue that is for the Tories.
He may also think that, with such an incentive, the DUP's eight MPs could be counted on to back him in a confidence vote, should he need them.
That could be a factor. But, in the final analysis, the figures will have to stack up for Britain, as well as for us.