He has been Leader of the Opposition in the Cortes of Castile and León since the 2015 elections, and was previously in the Congress of Deputies between 2008 and 2015.

[2] In October 2014, Tudanca became Secretary General of PSOE in Castile and León, receiving endorsements from former prime minister José Luis Rodríguez Zapatero.

[4] In May 2019, Tudanca's party the most-voted for in regional elections, but the PP and Citizens formed a government and installed Alfonso Fernández Mañueco as president.

[5] In March 2021, Tudanca tabled a motion of no confidence in Fernández Mañueco's government.

The motion failed, being supported only by the PSOE and two Podemos representatives, and abstained on by minor parties.