[6][7] Smith was elected the Women's Officer for Lancaster University Students' Union, a sabbatical role, and served in the 2006–2007 academic year.

[6] Smith first stood for election as a Labour Party candidate for University ward on Lancaster City Council in 2007.

[5] She supported John McDonnell for leader in the 2007 Labour Party leadership election which was occasioned by Prime Minister Tony Blair's resignation; Gordon Brown won unopposed.

[8] In the same year, she was a candidate for Labour Party National Executive Committee (NEC) Youth Representative.

[6] Smith won Lancaster and Fleetwood in the 2015 general election, defeating the Conservative incumbent Eric Ollerenshaw.

In the ensuing leadership election, Smith was a supporter of Jeremy Corbyn's candidacy and was one of 36 Labour MPs to nominate him for leader.

[16] She criticised the 2016 European Union referendum, saying that younger people preferred to remain in the EU, while the majority result was to leave.

[19] On 6 April 2020, Smith was re-appointed to her shadow cabinet role by the newly elected Labour Party Leader, Keir Starmer.

[citation needed] In addition to her other duties, Smith served as Shadow Deputy Leader of the House of Commons, in which role she made her debut at the Despatch Box on 20 December 2016.

[31] In 2010, Smith was diagnosed with postural orthostatic tachycardia syndrome (POTS), which she says has affected her energy levels, and which she uses medication to control.