As he contemplates David Cameron’s “big, open and comprehensive offer” to work together in government, Nick Clegg will tonight be carefully weighing whether it offers a once-in-a-lifetime opportunity or a deadly trap.
Liberal Democrats have long dreamed of a hung parliament where they would have real leverage to push through cherished policies - most notably the sort of electoral reform which would enable it to break out permanently from the third-party ghetto.
There is also the tantalising prospect - not directly mentioned by Mr Cameron - of seats around the Cabinet table for Mr Clegg and one or two of his senior colleagues, and maybe junior ministerial postings for a smattering of others.
The Conservative leader was at pains to play up the common ground between the two parties - the pupil premium, the low carbon economy, scrapping ID – while promising to take seriously the Lib Dem demands for a “fairer” tax system.
And perhaps most crucially of all, he acknowledged the need for reform of the voting system for Westminster elections, offering an all-party committee of inquiry.
For some in the party it will, no doubt, seem too good to refuse. Many, however, are likely to be wary.
One area where Mr Cameron made clear that he was not prepared to compromise was on the need for spending cuts this year, to begin tackling Britain’s record deficit - something the Lib Dems argue risks tipping the country back into a double-dip recession.
There is likely to be concern about the impact on the party in the country if they find themselves associated with the kind of draconian measures which most analysts believe that a Conservative government would have to introduce.
The proposal for a committee of inquiry on electoral reform will also be treated by suspicion by some. Plenty will remember that Tony Blair made a similar promise before the 1997 election, only to kick the resulting report, by
the late Roy Jenkins, into the long grass after it became clear that he did not need the Lib Dems’ support in Parliament.
However the alternative - throwing in his party’s lot with Gordon Brown and Labour - is likely to prove equally fraught with difficulties for Mr Clegg.
The Prime Minister was keen to stress that the Lib Dems were much closer to Labour when it came to reducing the deficit, agreeing that spending cuts should wait until next year.
He also underlined Labour’s manifesto commitment to a referendum on electoral reform, albeit on the more limited alternative vote system rather than the full proportional representation that the Lib Dems want.
But doing a deal with Labour would mean propping up an unpopular prime minister who has just led his party to their worst election result in 80 years, something the country at large may not understand or forgive.
Even if Labour were to ditch Mr Brown and find a new leader, it would not necessarily be any more palatable. A Labour-Lib Dem coalition would still lack an overall majority, leaving them dependent on the support of the smaller parties, such as the Scottish and Welsh nationalists.
Such an arrangement would be inherently unstable, and there would be huge questions over what it could deliver when it came to electoral reform, particularly as its basic legitimacy would be under constant attack from the Conservatives.
Other factors also may enter into the equation. At a personal level Mr Clegg may find it easier to work with Mr Cameron, having made little attempt to hide his dislike of Mr Brown.
Equally he knows that the Lib Dems and Conservatives are not exactly natural bedfellows and that a deal with the Tories could prove hugely divisive within the ranks of his own party.
Another option for Mr Clegg could be to allow Mr Cameron to govern as the leader of a minority administration, promising not to oppose key business, such as the budget and the Queen’s speech. But that may mean foregoing the best opportunity in a generation for the Lib Dems to exert real influence on the levers of power.
After the hype and hoopla “Cleggmania”, it was a return to earth with a bump for the Lib Dem leader as the enthusiasm generated on the campaign trail failed to translate into votes and seats.
For the sake of his party, he will now need to demonstrate judgment and assurance as he takes on his assigned role as the new “kingmaker” of British politics.