Hamon.
But if Macron made the runoff and I were French I'd yell things like "MON ROI EST VIVANT" in reference to him.
You tend to think about this, from what you've said yourself, like it's a Democratic primary. Sanders lost, so you can get enthusiastic about Hillary, since she basically represents the same option. However Macron v. Le Pen would be more like Chirac v. Le Pen. It's not voting "for", it's voting "against". Oh yes, I could see myself being enthusiastic about voting against Le Pen, while still dissapointed it was Macron who qualified for the runoff (same goes for Fillon, of course). If Hamon is your Sanders, then Macron would be Susan Collins at best, preferable to Trump but still, not my cup of coffee.