Private members games
Two layers of parliamentary game-playing should make Friday's sitting of the Commons an interesting affair.
It's the start of the private members bill season, with the first measure in the queue the Lib Dem Andrew George's Affordable Homes Bill.
The bill aims to introduce significant exemptions to the Spare Room Subsidy/Bedroom Tax, so it's a wedge issue within the Coalition - and its first place in the list of private members bills means its fate will affect later bills, so it will influence the fate of the third bill in the list, Bob Neill's EU Referendum Bill.
Labour see the bill as an opportunity to get the Lib Dems to disown the so-called "Bedroom Tax" (and quite a few Lib Dem backbenchers will be keen to do so) and will therefore support it, "as a rope supports a hanging man".
But with the Tory awkward squad expected to turn out in force to spin out the debate until time runs out ("does the Pope have a balcony?" one awkward squaddie responded, when asked if he would be there) a hundred MPs will be needed to close the debate and ensure the Bill receives a Second Reading.
Shadow Work and Pension Secretary Rachel Reeves is promising to support the bill at Second Reading: "I and other Labour MPs will be present in the House of Commons chamber to support the Bill so that it has the best chance of progressing through to its next stage. And in Committee we will do what we can to strengthen and extend its scope."
But getting sufficient support into Westminster on a Friday is a big ask as the election looms, and MPs become keener on spending more time with their constituents.
However, there is a second reason to tempt Labour MPs (and indeed Lib Dems) to give up their cherished constituency Friday....
If Mr George's Bill goes into committee, it will be first in the queue for a report stage debate, later in the year.... followed, if it, too, gets through second reading a week later, by Michael Moore's International Development Bill.
All of which means that the EU Referendum Bill - the third private members bill in the queue - cannot then return to the Commons for its Report Stage debate until December, at the earliest (and the moment could be delayed still further if there is a go-slow at Committee Stage).
The later the Referendum Bill returns to the floor of the House, the less time remains to get it through, before Parliament dissolves for the May 2015 election. Remember that the first incarnation of that measure - piloted by James Wharton - required three long days of report stage consideration, last year.
This time round, its opponents will want to prolong proceedings even further, because if the Referendum Bill survives un-amended it can then be forced into law via the Parliament Act, if it is amended or blocked in the Lords. So the debates on Mr George's Bill and Mr Moore's, while important in themselves, will also be preliminary skirmishes in the continuing EU referendum battle.
And, post Carswell, the Conservative leadership have to show their troops that they are completely committed to the referendum.
UPDATE: I'm hearing that the Conservatives will be on a three line whip for Friday - a highly unusual move. The game's afoot!