That would require some number-crunching. As a first approximation, and presuming that people's second preferences would correspond to how they habitually vote in a second round, it would eliminate nearly all of them. I was going to say it would eliminate all those except those which result in a triangular second round, but that's too big an assumption.

At a guess, it would largely solve the UMP's problem with triangular second rounds vs. the PS and FN, which will cost them dearly this time. If a majority of FN voters give their second preference to the UMP, this would probably tip the balance to elect the UMP candidate in the first round, in most cases.

Insofar as it gives more power to electors at the expense of the parties, it's a good thing I guess... though it hurts to say so.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}