Well, talking about Napoleon III, this thread should be in pre-1900 section.
Try this guy
http://en.wikipedia.org/wiki/Henri,_Count_of_Chambord
To make a long story short: Louis XVI had two brothers, Louis XVIII and Charles IX. All three were king of France, the last two in the 1815 - 1830 era.
Charles IX was the French monarchy last hope, and he had a son (that was assassinated in 1820) and a grandson, Henri, count of Chambord.
In 1870 when Napoleon III was crushed and the empire collapsed, France was on the brink of a constitutional monarchy, British style.
The 3rd Republic really took off after 1880. Thus for a decade there was a serious possibility (and the last in history in fact) to restore the monarchy.
Unfortunately for the monarchists, Henri V was an idiot that refused to make concessions to the Republicans.
The final straw was when he refused the tricolour flag in favour of the fleur-de-lys. That made a French constitutional monarchy impossible.
After 1880 a return to the monarchy in France is essentially ASB - even in 1914, and even more in 1940.
The monarchists numbers and influence seriously dwindled, After1890 their credibility took a huge hit with the Action Française - a hodgepodge of monarchism, anti-semitism, and conservatism (among many others tendencies). The Action Française last hurrah was Vichy France, which explain why the French have very little affection for monarchy today.