The fate of the government's proposed referendum on alternative vote (AV) hangs in the balance in the Lords today.
The coalition wants the referendum to take place on the same day as local and devolved elections next year.
Labour has lambasted proposals to redraw constituency boundaries contained in the bill as tantamount to political "gerrymandering".
Depending on today's events, the bill may be referred to a Lords committee where it could languish until the deadline for fixing the referendum by the Electoral Commission passes in February.
The coalition may still be able to force the matter in parliament, but only by creating separate legislation.