[1] He was elected as a president of Student Body Organization and became Corps Commander of Citizen Advancement Training I during his high school days in Laguna College of Business and Arts.

[1] Hernandez entered the field of public service in 1992 as Sanguniang Kabataan chairman of Barangay Mabato, Calamba, Laguna and won.

[5] He served for three consecutive terms from 1995 to 2004 and was also installed as the President of the National Movement of Young Legislators (NMYL) Laguna Chapter.

At the age of 34, Hernandez was elected as Vice Governor; the youngest ever in the history of the province to take over the position who got 160,368 votes.

[1] Even though he was still eligible to run for his second term, Hernandez pursued the governorship in 2010 while still being the youngest candidate in the province of Laguna.

The petitioner in the disqualification case is Edgar San Luis, who is the former Congressman of 4th district of Laguna and opponent of Ejercito for the 2013 gubernatorial race.

[8] The writ of execution disqualifying Ejercito as the Governor was served by the Department of Interior and Local Government (DILG) on May 28, 2014, at the provincial capitol in Santa Cruz, Laguna.

Some of his most significant contributions include: Additionally, Hernandez received the Gawad Parangal Award as an Outstanding Provincial Governor of the Philippines in the field of Social Welfare and Development from the Association of Local Social Welfare and Development Officers of the Philippines, Inc. (ALSWDOPI) in 2018, 2019, and 2020.