Is there a legally mandated filing fee and/or deposit in the last instance?
Mexico
ConstituciónPolítica de los Estados Unidos Mexicanos (published 1917-02-05, last amended 2014-02-10), http://www.diputados.gob.mx/LeyesBiblio/pdf/1.pdf
English versi?n (not updated): http://www.trife.gob.mx/en/consultations/political-constitution-united-mexican-states
Thereare never any fees or deposits for complaints filed with the Electoral Tribunalof the Federal Judiciary.
Article9 lists all required elements of a complaint. No fee or deposit is mentioned.