[5][6] In 1999 he served as a member of Prime Minister John Howard's No campaign during the republic referendum.

[7] Leeser worked as an adviser for Minister for Workplace Relations Tony Abbott in 2001 and for Philip Ruddock between 2004 and 2006.

[17][18] He resigned from shadow cabinet in April 2023 after the Liberal Party resolved to support the "No" vote at the 2023 Australian Indigenous Voice referendum.

[20][21][22] Leeser supports Australian recognition of West Jerusalem as capital of Israel, as implemented by the Morrison government in 2018.

[23] The following month, he and deputy Liberal leader Sussan Ley travelled to Israel to "reaffirm the Coalition's commitment to West Jerusalem as the nation's capital", in a trip organised by the Australia/Israel & Jewish Affairs Council.

[25] He subsequently announced that he would wear a kippah in federal parliament for one week as a statement against increased anti-semitism in Australia.

[27] In January 2025, following a rise in antisemitic incidents in Australia, Leeser called for mandatory jail sentences for people convicted of vandalising Jewish sites, stating that "people need to know that if you graffiti a synagogue or a Jewish communal property, you will go to jail".