Nick Clegg and his advisers have something they like to call the "mirror test". Imagine looking yourself in the mirror in 2015, asking what you've achieved and deciding whether you're happy with it. Clegg fears that if he hasn't brought about reform of the House of Lords by the end of this Parliament, he won't be able to look himself in the mirror again. Come 2015, though, he may find himself wondering why he ever tried to finish what his Liberal predecessor, Herbert Asquith, started. For if he persists, he's likely to become bogged down in Parliament, despised even more by voters, and possibly even shafted by his coalition partner.
Clegg keeps reminding his Conservative colleagues that this year is the centenary of Asquith's great Parliament Act of 1911, which first curbed the Lords' powers. He also reminds them that every Liberal manifesto since then has promised to reform the Lords further. The Tories, so far, are playing along with him, and he will present a draft Bill and a White Paper to the Commons tomorrow. But the real danger for him is that he is taking on an issue that has no voter appeal and looks, like AV, to be another self-interested way of getting more Lib Dems into Parliament. At least, in 1911, the Liberals could argue that the Upper House posed a real problem. Two years earlier, the Lords had refused to pass Lloyd George's Budget, which included land taxes on the rich. Even after the Liberals had twice been re-elected, their lordships showed no signs of respecting the Commons' political legitimacy. So the reforms, when they came, were a means both of breaking the parliamentary gridlock and ensuring that an unelected House could not thwart the will of the people again.
Today is different. What is the problem to which Lords reform is a solution? It's true that if you were designing a second chamber, you might not start from here; but in practice, the upper house works remarkably well. It is packed with eminent experts who scrutinise legislation with a specialist eye. These are high-grade people who wouldn't demean themselves to stand for election. Can you imagine Lord Guthrie, former Chief of the Defence Staff, pounding the pavements with a sheaf of party political leaflets? Or Lord Butler, former Cabinet Secretary? Or the philosopher Baroness Warnock? This is the sort of expertise we would lose if we were to move to an elected second chamber.
David Cameron's difficulty with the NHS reforms is that people aren't convinced that the NHS needs fixing and they distrust his motives for imposing change on it. Messing with the Lords will, in the same way, make Clegg look out of touch: obsessed with reforming something that seems to be working perfectly well at a time when most voters are worried about losing their job or making their wages last the week. And they will think it very odd that he proposes to introduce proportional representation to the second chamber when they've just trashed proposals to introduce it to the first.
Cameron has told his coalition partners that he will strongly support Clegg and will emphasise that this is a policy of the whole Government, not just the Lib Dems. But there are rumblings not much further down the hierarchy. One Cabinet minister, who is in other respects a moderniser, told me yesterday: "In the scale of things, this is about 27th-order importance." Another said, "If we'd won a majority, this wouldn't be our priority." It's not that the Tories, with a few exceptions, are wildly against reform. They just don't think it's worth the parliamentary hassle.
Even Clegg has recognised, since the AV referendum, that he shouldn't appear wildly enthusiastic about another piece of constitutional tinkering. He'll be getting his junior, Conservative, minister Mark Harper, to take the legislation through the Commons when it happens. And Lord Strathclyde, the Tory Leader of the Lords, will be in charge there. "We'll be doing this in quite a sotto voce way," says a senior Lib Dem. As a result, tomorrow's draft Bill and White Paper are likely to offer options for an 80 or 100 per cent elected Upper House, rather than insisting on the 100 per cent that Clegg wants. These will then go to a joint committee of both Houses, with parliamentarians of all parties, crossbenchers and bishops, who will take at least a year to chew them over. Then it will be for the Government to decide whether to try to push the legislation through a possibly quite unco-operative Parliament.
Clegg knows that if he is to have any chance of success, he needs full- hearted backing from Cameron. He might get this tomorrow, but will that loyalty last through three or four years of squabbling, unpopularity and opposition from some Tory backbenchers and peers? The Prime Minister's behaviour over AV is not a good precedent. Cameron started by promising Clegg that he would take a back seat in the AV referendum campaign. Pressured by his party, he went back on that assurance, and his intervention almost single-handedly turned the campaign round. Some Lib Dems think he wouldn't dare to let them down like that twice: "Having gone through the difficult period of AV," said one yesterday, "if he's seen to be going cold on this, he knows how bad that would be for coalition relations." But others are more sceptical.
Meanwhile, the Labour Party is split on Lords reform and, even if Ed Miliband could deliver support in the Commons, he doesn't seem able to control his Lords. In 1968, a coalition led by Enoch Powell from the right of the Tories and Michael Foot from the left of Labour managed to scupper a Lords reform deal that their own party leaders had agreed. If enough Tory MPs and Lords are opposed to Clegg's proposals, they could team up with Labour allies to do the same.
The Lib Dems are nervous already. They have noticed that when leading Tories talk about this issue, they often use two telling words: "bring forward". The Coalition agreement only commits the Government to "establish a committee to bring forward proposals for a wholly or mainly elected upper chamber on the basis of proportional representation." This is not the same as a wholehearted commitment, including using the Parliament Act to make sure it happens even if the Lords vote against.
"To stop there would be an act of bad faith," insists a Clegg ally. "Using those words suggests to the public that you have a serious intent to push the reforms through." But he acknowledges that even some on his own side are having second thoughts. After all, Lib Dem MPs who fear losing their seats at the next election might rather like to be appointed to the Lords benches instead. If the reforms go through, they wouldn't be allowed to stand for election to a new Upper House.
It's certainly not going to be easy, as one supporter acknowledges. "Getting a Bill about the Lords through the Lords is the political equivalent of water torture. You've really got to want to do it." So the question for David Cameron, as he looks in the mirror this morning is: does he really want to do it? And the question for Nick Clegg ought to be: is this really such a good idea?