Who is the only reigning monarch to be elected in regular intervals by popular vote?

Explanation

The Principality of Andorra, is a small landlocked country in southwestern Europe, formed in 1278. The role of monarch is exercised jointly by the two co-princes, the President of the French Republic and the Bishop of Urgell, Catalonia, Spain. This peculiarity makes the President of France, in his capacity as Prince of Andorra, the only reigning monarch actually elected in regular intervals by popular vote, though not by the people of Andorra.