Born on 28 March 1986 in Madrid, Espinar is son of Ramón Espinar Gallego, Spanish Socialist Worker's Party politician who served as 1st President of the Assembly of Madrid between 1983 and 1987.

[1] He collaborated in LaTuerka (a TV show presented by Pablo Iglesias Turrión) and worked as researcher for the UCM.

[1] He ran 3rd in the Podemos list for the 2015 Madrilenian regional election, and became a member of the 10th term of the Assembly of Madrid.

In November 2016 he participated in the party primary election to select their leader in the Community of Madrid.

After a party crisis in January 2019, following the announcement of Íñigo Errejón vowing to run as candidate for the 2019 Madrilenian regional election within the Más Madrid platform, Espinar renounced to his parliamentary seat at the regional legislature (and therefore also to his seat as senator) as well as handed in his resignation as leader of Podemos in the Community of Madrid and the rest of his roles at the party, arguing the conditions to carry the Podemos project in Madrid towards where he thought it should be driven towards were not there.