The basic difficulties for the formation of a coalition, as I view them, are three :
1st: there is an issue of credibility. The PN is not credible when it speaks against corruption and in favour of good governance, unless it clears the deck and solves its current issues, as highlighted in my article published today: Coalition building: beyond the arithmetic.
2nd : there is the format in which a coalition could take shape: forming part of the PN is no coalition at all, it is also not acceptable to AD; it is possible to form a separate structure specifically for the elections, but time is running out for such an option;
3rd : there are various issues of policy in respect of which there may be sharp disagreement, particularly in respect of environmental issues. The proposed tunnel between Malta and Gozo, and the proposed car-racing track as well as spring hunting, all of which are supported by the PN but which are objectionable in principle to AD readily come to mind. There are also a number of other issues of a social and economic nature which could also be contentious.
All the above requires considerable time and goodwill, both of which are in short supply.
(The above is a reply I gave on one of my blogposts in reply to a question by Prof. Josef Lauri earlier today.)