Barracciu entered politics in the 1980s, militating in the Italian Communist Party (PCI). In the 1990s, she joined the PCI's legal successors parties, the Democratic Party of the Left (PDS) and then the Democrats of the Left (DS). A member of the Democratic Party (PD) since its foundation in 2007, she was regional secretary of Sardinian PD from July to December 2008. She has been assessor and municipal councilor of the municipality of Sorgono, as mayor of the same municipality from 2005 to 2010 (elected with 100% as the only candidate); she also was Regional Councilor of Sardinia from 2004 to 2013. In 2009, Barracciu ran for the European Parliament in the ranks of the PD in the Italian Islands constituency and obtained 116,844 preferences, making her the first of the non-elected, and then taking over from Rosario Crocetta on 17 December 2012, after his resignation for the election as president of Sicily.
On 29 September 2013, Barracciu won the centre-left coalition primary election in the first round ahead of the 2014 Sardinian regional election with 44.3% of the vote and 22,808 preferences. On 30 December 2013, after some pressure from members of her party, she renounced to participate in the electoral competition, as she was investigated in the investigation into the expenses abuse of funds to regional groups, and was therefore replaced by economist Francesco Pigliaru, later elected president of Sardinia.
On 28 February 2014, Barracciu was appointed Undersecretary of State at the Ministry of Cultural Heritage and Activities and Tourism led by the minister Dario Franceschini, resigning as MEP, ratified on 11 March 2014. Her appointment caused serious perplexity as Matteo Renzi himself, at the time new secretary of PD, asked Barracciu to renounce the race as a centre-left coalition candidate for the presidency of Sardinia despite the victory in the primary, two months from the vote, because investigated for the use of regional funds. Renzi and the Minister of Reforms Maria Elena Boschi defended the appointment of Barracciu, and other undersecretaries under investigation, reiterating that the guarantee notice should not be judged as a definitive sentence.
In 2015, Barracciu ran for city councilor in Sorgono in support of the mayoral candidate Vincenzo Rodi and his list A Future for Sorgono. The list was not successful, as the left-wing civic list candidate and CGIL trade unionist Giovanni Arru was elected mayor, and his Unita Mente list obtained 68% (789 votes), surpassing Rodi stopped at 33% with 372 votes; with 88 votes, Barracciu with 88 votes was the most voted on the losing list after the mayoral candidate by entering the city council.
In November 2019, Barracciu left the PD and joined new Renzi's political party Italia Viva (IV).[2][3]
