.....After joining the coalition poll ratings for the party fell,[85] particularly following the government's support for raising the cap on tuition fees with Liberal Democrat MPs voting 27 for, 21 against and 8 abstaining.[86] The Liberal Democrats had made opposing tuition fees a major message of their campaign, with all of the party's MPs, including Nick Clegg, signing the Vote for Students pledge to oppose any increase in student tuition fees prior to the 2010 general election.[87] Clegg later made a formal apology for breaking this promise in September 2012.[88][89] Shortly after the 2015 general election, Liberal Democrat leadership contender Norman Lamb conceded that Clegg's broken pledge on university tuition had proven costly.[90] ...
The Lib Dems lost over 300 councillors in the 2012 local elections, leaving them with fewer than 3000 for the first time in the party's history.[97] In June 2012 it was reported that membership of the party had fallen by around 20% since joining the coalition.
Wiki: https://en.wikipedia.org/wiki/Liberal_Democrats_(UK)#Nick_Clegg_and_coalition_with_the_Conservatives_(2007%E2%80%932015)