Errm, they DON'T.
IF Lib Dem join with no one, whose installed? yes, the winner of the election, the Torys.
I wish people KNEW what they were talking about.
Torys WON the election, however its a constitutional right that the encumbant PM can TRY to form a coalition that would provide a majority count of seats in the house.
That has NOTHING TO DO WITH THE ELECTION.
If Labour and Lib dem get together, they have the PM and the majority in the house, TORYS STILL WON THE ELECTION.
They are simply not the same thing, the election has been, and gone, Torys won, what happens after is part of well, how our government is run, it is not the election, they are two separate things.
If no coalition is formed at all between anyone, Torys take the seat, Tories can form the government with THEIR CURRENT NUMBER OF SEATS if Lib Dem and Labour don't form a coalition government. The only reason they are actively courting Lib dem, is to prevent them joining with Labour. If Clegg just came out and said theres no way in hell he'll join Labour, Torys would be in No 10 tonight. However its not in Clegg's interest to make it clear he won't join Labour, because while the question is still unanswered he'll be offered everything but the shirt off Cameron/Browns back to NOT join with the other side.