France’s Glucksmann notched a crushing primary victory. But he needs more allies to win the presidency.

PARIS — Raphaël Glucksmann’s unexpectedly decisive victory in France’s center-left primary may have won him the backing and resources of the once-powerful Socialist Party, but the 46-year-old MEP needs even more support if he wants to drive his distinctly pro-European platform all the way to the Elysée Palace. All recent polls show Glucksmann is trailing far-right front-runner Marine Le Pen and her two main challengers for a spot in the presidential election’s second round: the far left’s Jean-Luc Mélenchon and center-right former Prime Minister Edouard Philippe. Mélenchon and Le Pen both want to fundamentally alter Paris’ relationship with Brussels, while Philippe is campaigning mostly on domestic issues.