Ó Broin was elected to
Belfast City Council in
2001, stepping down in 2004. He was the National Organiser of
Ógra Shinn Féin between 1995 and 1997. He was Sinn Féin's Director of European Affairs co-ordinating his party's team in the
European Parliament in
Brussels, from 2004 to 2007. He is a former member of Sinn Féin's governing body and a regular columnist with the republican newspaper
An Phoblacht. He campaigned against the
Treaty of Lisbon and spoke at the
National Forum on Europe on behalf of Sinn Féin and the No 2 Lisbon campaign. He is also a published writer. His first book,
Matxinada - Basque Nationalism and Radical Basque Youth Movements was published in English in 2004 and in Spanish in 2005. His second book,
Sinn Féin and the Politics of Left Republicanism was published by Pluto Press in 2009 and the launch was held in Pearse Street Public Library on 16 February 2009. Ó Broin is also the editor of
Left Republican Review. As a freelance writer he has articles published in
An Phoblacht,
Magill,
Village Magazine and
The Irish Times. He was an unsuccessful Sinn Féin candidate for the
Dún Laoghaire constituency at the
2007 general election. He ran for
Dublin Mid-West at the
2011 general election. He polled 5,060 votes being beaten to the last seat in the constituency by
Derek Keating of
Fine Gael. He subsequently declared his intention to run for the
Seanad, and was defeated in his election campaign. In 2013, Ó Broin was co-opted by Sinn Féin onto
South Dublin County Council to represent
Clondalkin local electoral area, after sitting councillor Matthew McDonagh resigned his seat. In the
2016 general election, he topped the poll in the
Dublin Mid-West constituency with 22.7% of the
first preference votes, and was elected on the first count.
Mark Ward was co-opted to fill Ó Broin's seat on South Dublin County Council. In May 2019, the election of
Frances Fitzgerald TD as a
Member of the European Parliament created a vacancy in the Dublin Mid-West constituency. At the resulting
by-election in November 2019, Ó Broin managed the campaign of the Sinn Féin candidate
Mark Ward. Wards's victory gave Sinn Féin two of the constituency's four seats. At the
general election in February 2020, Ó Broin again topped the poll, with 26.1% of the
first-preference votes. He was again re-elected on the first count, and his transfers secured Mark Ward's re-election on the second count. , Ó Broin is Sinn Féin's spokesperson on housing. Housing proved one of the key issues in the
2020 Irish general election and factored into Sinn Féin's significant gains in the voting. ==Personal life==