Marius is one of those people who throws himself whole-heartedly into his beliefs, especially when they reverse.
He grows up in a Restoration-friendly household that hates Napoleon, the Republic, and the Empire, but when he discovers they’ve lied about his father, who was a decorated soldier under Napoleon, he completely throws himself into supporting the Republic, to the extent that he embarrasses himself in front of his friends who, while they support the ideals of the Republic, aren’t too fond of Napoleon.
Later on he ties all his well-being to his hoped-for life with Cosette, going from the heights of happiness when they’re together to the depths of complete and utter despair when he fears he’ll never see her again.
On Tumblr (Re-Reading Les Mis)