Actually I stand corrected...
France is different from most european countries - it doesn’t have a parliamentary form of government. They have a “strong president” type of government, more like ours. The president is elected by a majority of popular votes and he then appoints a prime minister.
Given that, the level of influence the muslim party would have over who becomes president will be limited to...
1. voting with the socialists
2. voting for the more conservative party
3. abstain
My guess is that they’ll side with the socialists
Though they will get some seats in the parliament. And probably in another 20-30years they mat be able to contend for the presidency
But then again maybe the muslim party will drain enough votes from the Socialist candidate that he nor they will make the run off. Still it will complicate the races in the assembly as I mentioned.