 Once Primo de Rivera replaced the liberal restauración with dictatorship, Bau enthusiastically engaged in the nascent primoderiverista structures; in 1924 he co-founded the Tortosa branch of Unión Patriótica and became its jefe provincial.During the period called "Bauisme" in the history of Tortosa, in 1925 Bau was unanimously elected mayor of the city, re-elected in 1928 and holding the post until 1930.His contribution was multifold; during 5 years the Bau-led ayuntamiento executed the plan of public works, consisting of modernization of city streets, refurbishment of public schools and hospitals and setting up regular fire brigade services.