At the moment, it is reasonable to assume that the price of Britain's political system would appear to be some sort of governing coalition of the Tories and Liberal Democrats. This might take the form of a formal blue/yellow alliance, with LibDems in a Tory cabinet; or it might mean LibDem support for the Tories on certain votes (the next budget, for example) and abstention on certain issues. In any event, Gordon Brown and Labour have been unquestionably rejected, and any arrangement between Brown and the LibDem leader Nick Clegg to keep the Conservative leader David Cameron out of No 10 Downing Street would lack legitimacy, and lead to a strong rebuke at the next general election--probably in a year.
Obviously, this is all a mixed blessing for Conservatives, and there is an argument (with which I don't agree) that because governance in the short term will require painful and unpopular decisions on public spending, it might be wise for the Tories to let Brown and Clegg do the dirty work.
One encouraging note, however, is the disappointing performance of Clegg and the Liberal Democrats, who seem actually to have lost seats. Having embraced the worst aspects of American political practice with three televised 'debates' Britain's chattering classes embraced Clegg as the putative winner of the debates, and elevated him to Obama status: A charismatic savior of the national soul, a saintly post-political (but safely left-wing) balm for Britain's ills. Thankfully, if the British electorate did nothing else in any definitive way on Thursday, it rejected the notion of redemption by Clegg--and rebuked the political and cultural elites which had ordained him and the LibDems.