That is apparently what Peter Robinson thinks the European Parliament election on 4 June actually is.
At the launch of the DUP manifesto, Peter Robinson gave a speech in which he said that: "The European election is the only Province-wide poll and is regarded as a test of Northern Ireland’s constitutional position."
So the cat, never well hidden, is out of the bag. The DUP really do see all elections as part of the constant process of constitutional referenda. They are right, of course, but nonetheless it must be worrying them, as election after election sees unionism's slim lead being whittled away.