On November 4, 2014, Hadley defeated Democratic assembly member Al Muratsuchi by a margin of just 706 votes in an upset.

[6] In June 2012, Hadley was elected to the board of the Republican Party of Los Angeles County, representing the 66th Assembly District.

[8] In September 2016, Hadley announced he would not vote or support the Republican nominee for the presidency, Donald Trump.

[11][12] In 2015, Hadley authored AB 306 to give the children of military personnel better options in choosing which school district they matriculate into, regardless of on-base housing's location, which was signed into law.

[13] He worked with environmentalist Erin Brockovich to increase awareness of water quality in the city of Gardena in 2015–16.