Khandro...its my belief that Cameron had no option but to go into a coalition
with the LibDems in 2010. The LibDems, however, did have a choice but decided to sup with the Devil without using a long enough spoon, thus signing their death warrant for a generation or two at leadt.
The arithmetic show how parlous Cameron's position would have been if he had tried to go it alone. He may have had to call an election long before 2015 and it is by no means certain that if he done that, he would have won a clear majority.
The Tories were fed up with, and not used to being in the Opposition by the time 2010 came along. True, the coalition was hardly an unmitigated success, but what coalition ever is ? Even the wartime coalition resulted in a huge Labour landslide victory in 1945, throwing out Churchill, who most believe was a great war-time Leader.
Cameron's victory in 2015 is not wholly but mainly due to him winning in 2010.