In 2019, he earned a master's degree in constitutional law and human rights at the Centro de Estudios Jurídicos Carbonell.

[5] In April 2013, Máynez announced that he was joining Citizen's Movement and contending for municipal president of Guadalupe in the 2013 Zacatecas state elections.

On 29 July 2021, Máynez was unanimously designated as the parliamentary coordinator of the Citizen's Movement caucus in the Chamber of Deputies for the LXV Legislature.

[14] In response, the deputies stated that the trip was self-funded, and Máynez emphasized that he was working on legislation related to security issues in Mexico.

However, on 2 December 2023, García withdrew from the race due to a political crisis over the appointment of an interim governor to replace him, prompting Citizens' Movement to select another candidate.

[29] Positioning himself as an alternative to Claudia Sheinbaum and Xóchitl Gálvez,[30] Máynez focused on appealing to younger voters,[31] frequently visiting universities during the campaign.

[32][33] Polling initially indicated that Máynez was the least known candidate out of the three,[34][35] with low recognition until the first presidential debate on 7 April, where he went viral due to memes about his constant smiling.

By the end of the campaign, many polling companies noted that Máynez experienced the most growth in recognition and support,[37] ranking second in approval, behind Claudia Sheinbaum but ahead of Xóchitl Gálvez.

[38][39] Throughout the campaign, leaders of Fuerza y Corazón por México repeatedly urged Máynez to step down and join their coalition, which he rejected.

[42] Luis Donaldo Colosio Riojas, a member of Citizens' Movement, urged either Máynez or Gálvez to withdraw in support of the other to form an opposition to Sigamos Haciendo Historia.

[43] On 22 May, a campaign event attended by Máynez for the Citizens' Movement mayoral candidate in San Pedro Garza García, Nuevo León, saw the stage get toppled by strong winds while he was speaking, killing ten people and injuring 213 others.

Máynez conceded after the INE's Quick Count announcement, highlighting that the results represented the best performance for Citizens' Movement in a presidential election.