There is at least one other person in the world, besides me, who is actively searching for the first country to have a semi-presidential constitution. I know because I met such a person at a conference recently. (We had other things to talk about too, honestly).
We both agreed that Weimar Germany was the first we had discovered. The Weimar constitution dates from August 1919. However, it is possible that there is an undiscovered semi-presidential predecessor out there.
One example that I explored recently was the case of France in 1848. I have done some work on France, but I am not a historian and I am not familiar with this period of French history.
Anyway, as I understand it, in November 1848 a new Constitution was adopted – the Constitution of the Second Republic. The text is available in French at the website of the Constitutional Council. I do not know of an English translation. The articles that approximate semi-presidentialism are as follows:
Article 45: “The president is elected for four years …”
Article 46: “… The president is selected (nommé), by a secret ballot and by an absolute majority of voters, by direct universal suffrage of all the electors in French departments and Algeria”
Article 70: “There is a vice-president of the Republic selected by the National Assembly from the three candidates presented to it by the president in the month following the [presidential] election.”
In their article in Electoral Studies (vol. 16, no. 4, 1997, p. 442), Blais et al say that this was the first time a major European country had made provision for a direct presidential election. The first election was held on 10 December 1848 and was won by Louis Napoléon Bonaparte with nearly 75% of the vote.
Interestingly, from a semi-presidential point of view, even though there is no mention of a prime minister in the Constitution, world.statesmen.org – my usual source of these things – indicates that there was a prime minister – Camille Odilon Barrot – for nearly a year after the introduction of the Constitution before the post was abolished on 31 October 1849. He was appointed on 20 December 1848. I do not know whether Barrot was selected by the Assembly in the manner provided for by Article 70. I do not know whether there was a vice-president selected by the Assembly.
There are a couple of reasons why France 1848 was not semi-presidential:
1.) There is no mention of a prime minister in the Constitution;
2.) The provision for direct election was not absolute: Article 47 states: “…If no candidate obtained more than half of the votes cast, and at least two million votes, … the National Assembly elects the president of the Republic, by an absolute majority and by secret ballot, from the five eligible candidates who obtained the most votes”.
Also, there seems to be no collective governmental responsibility to the Assembly.
So, the French Second Republic is not the first case of semi-presidentialism, but it does have some interesting semi-presidential-like features. I am still exploring whether semi-presidentialism may have occurred briefly in a Latin American context prior to 1919. But, so far, it seems that the first semi-presidential country remains Weimar Germany in 1919.