If the Tories get the most votes and the most seats, as all the polls today suggest they will, Cameron will end up as Prime Ministers. The Lib Dems have said too often that the party with the most votes and the most seats has a mandate to govern to go back on that.
The two big questions of the last few days are can Cameron close strongly enough to eke out a majority and can the Lib Dems hold on to second. There are reasons to think that the Tories will get over the line, their vote is solid and they are the party that is picking up support. Tory candidates in the battleground seats are also bullish about their chances. But I don’t think we’ll be able to predict the result with any confidence until the actual votes start being counted.