I think that's probably enough for the LD's, I can see Clegg selling it to the party as a precursor to more comprehensive voting reform perhaps?
Once people get used to voting for more than one person (assuming AV is voted for) then it's a much smaller step to shift towards STV/MMP than from FPTP direct.
There's no benefit whatsoever to the LDs agreeing to AV without a referendum - if they didn't believe reform was popular I don't believe they'd be pushing for it so strongly.
That said, if Labour offered a referendum on full STV/MMP then that could change things again.
It is, however, pretty funny, that the Tories now support 'fiddling the system' (their own words) against them.
Labour don't have the majority for full STV/MMP, even as the rainbow coalition, many in their party hate it.
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