The issue is and has been for some years that the attitude is "Won't vote Lib Dem as they won't win" and that voting Lib Dem in many constituencies can often take votes away from Labour (who are usually second) and so giving the Conservatives more seats. Hence the joy that is tactical voting.
In my constituency at least, Lib Dems used to be a very strong 2nd place to the Conservatives. In 2010 it was 50.4/37.7%, in 2005 it was 44.5/39.3%, 2001 was 46/34%, 1997 was 45/37.2%. So voting Lib Dem in those years at least might have made a difference.
Last election though? 2015 results, 56.1% Conservative, 14.4% Ukip, 13.4% Labour and just 9.7% LibDem. They used to be a strong second, in 2015 they dropped down beind the other two who were perennial also-rans.
So LibDems have a fair amount of support that just ran away in 2015, and considering we sadly voted fairly overwhelmingly in favour of Leave, LibDems won't be getting a whole lot of votes back in my area if they are campaigning on stopping Brexit.
That cost the party hard (and I largely disagree with that baclash) and will for years probably. They did some useful things in that coalition but that will mostly be ignored because they bargained away student fees in order to get it done.