The result, all too often, is that political expediency takes over. And so it was that although the principle of the legislation passed with a comfortable majority in the Commons on Tuesday night (despite a 91-strong Tory rebellion), when it came to the technicalities of timetabling the consensus came unstuck. With the rebels' ranks to be swelled by Labour, the Coalition faced a sure defeat, and the all-important "programme motion" was dropped.
The withdrawal may save the Government a shred of dignity. But in practical terms, the effect is much the same as if the vote had gone ahead and been lost. Either way, the outcome is catastrophic. For Nick Clegg, it undermines still further the attempts to persuade Liberal Democrat activists (and, of course, voters) that there is anything to show for propping up a Conservative-led coalition. For David Cameron, the fiasco is the clearest sign yet that he is losing control of his back benches, that the instinctive rebellion of the Eurosceptic fringe is seeping into all areas of the party. With the prospect of a reformed House of Lords more remote than ever, however, it is Britain's democracy that is the biggest loser of all.
The question, then, is what next? As things stand, a timetable will be put to the vote again in the autumn. The suggestion is that Mr Cameron may, by then, have his MPs in line. But it is far from clear what new pressure he can bring to bear on the recalcitrant, or if he really wants to. Meanwhile, the Deputy Prime Minister must review his options. He can water down his plans, to woo the Tories. He can try to address some of his Labour opponents' more substantive concerns, agreeing to a referendum, say. Or he can stick with the existing Bill, and extend the timetable so there is more opportunity to debate and amend it.
It is here that Labour comes in. The Opposition's position is, to put it kindly, a nuanced one. Ed Miliband is outspokenly pro-reform, hence Labour MPs' "aye" in the second reading vote. Hence, too, the charges of opportunism prompted by its rejection of the programme motion. With Lords reform putting unprecedented strain on the Coalition, it is hard to avoid the conclusion that, given the opportunity to turn the knife, principle was sacrificed for a quick, political win.
Not so, according to Labour insiders. Constitutional changes are too complex and too far-reaching to be rushed through the Commons in 10 days, they say, pooh-poohing Mr Clegg's claim that the "guillotine" is vital to ensure opponents do not talk the Bill to death. Perhaps. But the result is undeniable: Lords reform is all but off the table.
There is a straightforward way to resolve the matter: Mr Clegg must call Labour's bluff. After nine months with a cross-party committee, the substance of the Bill should remain unaltered. If the time allowed for debate was too short, it must simply be extended. Ed Miliband's aides claim he does not want the best to be the enemy of the good. Mr Clegg must give him the opportunity to prove it.
Whatever else, the reforms cannot be allowed to founder. Not because the Coalition will totter. Not because the Liberal Democrats will struggle to bear the loss. But because, arcane as it may seem, if we miss this opportunity then the blot on our democracy of an unelected second chamber will remain for another generation. It is to this that Mr Miliband must bend his mind.
