Unknown just three years ago, and with a party only 12 months old, Emmanuel Macron has seized the French presidency against all the odds. His challenge now is to govern.

To do that he must build a parliamentary majority that supports his election pledges in June legislative elections, when France's two established parties will put their huge machines to work.

Macron has at least one thing in his favor: the "majority amplifier" effect of an electoral system designed by postwar leader Charles de Gaulle specifically to maximize presidential independence from parliament.