Comment: Despite the possibility that the far-left party of Mélenchon may win the first round, it is still  unlikely, with Macron holding a two to three percentage point lead. There is virtually no chance of LePen winning the second round according to every poll, even if she is successful in the first round, which is also uncertain. 
So in fact if anyone except Mélenchon wins the first round, only candidates that are pro-European Union will be in in the running against LePen if she wins round one. Hence, there is a strong opposition. 
Likewise if any of the other leading candidates have a runoff against Mélenchon, it's still likely that he will lose. 
I wouldn't call the EU dead quite yet.