On the launch of the cross-party Yes Scotland campaign in 2012, Somerville was announced as its director of communities. She later stood as the SNP candidate in the Dunfermline by-election, 24th October 2013, coming second behind Cara Hilton of Scottish Labour. She did not return to her position in Yes Scotland after the by-election. She campaigned in favour of Scottish independence in the run up to the 2014 referendum.