He derailed a bill that would have added a gender-neutral option to Massachusetts driver's licenses, forced the state to reveal that it gave out $1.8 billion in public assistance to undocumented immigrants, and led an unsuccessful effort in the state legislature to remove Salem Superior Court Judge Timothy Feeley from the bench.

Lyons announced his intention to run for chair on December 19, 2018, after Geoff Diehl, a political ally, declined to seek the position.

[21] Diehl's endorsement of Brent Andersen, the party's treasurer, for the position resulted in criticism from more conservative members, including Lyons.

[27] During Lyons' tenure the party lost nine seats in the state legislature[28] and saw it reach its lowest share of registered voters since 1948.

[29] Karen Spilka mockingly proposed Jim Lyons Day for "his unparalleled contribution, helping us drive all the Republicans out of the State House".

[31] Donnie Palmer, a candidate in the 2021 Boston City Council election, was endorsed by Lyons and the Massachusetts Republican Party spent $3,697 on ads for him.

[35] Former party chairs Darrell Crate, Brian Cresta, Kerry Healey, Jean Inman, Jeanne Kangas, Jennifer Nassour, and Peter G. Torkildsen signed a letter calling for his resignation.

[36][37][38] 16 donors threatened to stop supporting the party if Lyons remained as chair and offered to raise $1 million if he was removed.

"[40] As the controversy continued to embroil Lyons, national Republicans distanced themselves from the MassGOP, with Congressman Dan Crenshaw and Congresswoman Cynthia Lummis canceling several previously planned fundraisers for the state party.

[41][42] By September, former White House Press Secretary Ari Fleischer had backed out of a heavily promoted party fundraiser "due to a conflict" with no new date having been announced.

[47] Lyons spent $1,800, $800 of which were party funds, to investigate Republican committee members, Lindsay Valanzola and Matthew Sisk, who opposed him.

[49][45][50] In 2020, Lyons requested the Internal Revenue Service, FBI, Federal Election Commission, Office of Campaign and Political Finance, and U.S. District Attorney Andrew Lelling to investigate Cook misusing $1 million in party funds.

[61] Lyons and Diehl proposed legislation to require people seeking welfare benefits to present a Social Security number or green card.