First up, going into coalition will inevitably drag them to the Right. I don't just mean the compromises that they have had to make to reach a deal with the Tories. This coalition has clearly strengthened the position of those who emphasize economic liberalism over social justice. That is, of course, a perfectly respectable intellectual position, but still, it's clear which wing is winning.
Secondly there are a couple of psychological factors I reckon will come into play. The first is status quo bias, whereby Lib Dem supporters, councillors, MPs will simply get used to where they have repositioned themselves on the political map. It will become their new 'normal'. The second is cognitive dissonance. Many Lib Dem supporters, faced with what looks like facilitating a right-wing government that increases inequality, will talk themselves into justifications. This may include convincing themselves that they were always really more about economic liberalism than social justice.
The latest stuff on UK polling report may bear this out a bit:*
In their final poll before the 2010 election YouGov asked respondents how they would have cast their second preference votes if they had been voting under AV.
Amongst Conservatives voters 45% would have given their second preferences to the Lib Dems, 5% for Labour, with the rest not sure, not casting a second vote, or casting one for minor parties. Amongst Labour voters, 6% would have given their second preference to the Conservatives, 64% to the Lib Dems. Lib Dem voters would have split their second preferences in favour of Labour by 42% to 27% for the Tories.
YouGov repeated the same experience at the end of June. Second preferences now break differently. Conservative voters are much the same, but Labour voters are now much less likely to transfer to the Lib Dems, from 62% at the election, now only 33% of Labour voters would give their second preference to the Lib Dems. Lib Dems now break in favour of the Conservatives rather than Labour, though not by very much (38% to 33%).
Not surprisingly, Labour voters are far more wary now of giving their votes to ...ahem... 'Gideon enablers'. But look at the Lib Dems starting to swoon in the Dark Side's embrace. Now the reason I put '*' is, as the post goes on to point out, that left-leaning Lib Dem voters may no longer be Lib Dem voters. So you'd expect some shift toward the Tories in second preference votes. But then that is just another tick in the box for a turn to the Right.
Now again, this is all perfectly reasonable. There is no reason why there shouldn't be a genuinely liberal right-of-centre party. But a) if that really what all those Lib Dem supporters thought they were voting to create b) are we convinced that the electoral system is the only thing that prevented such a party from emerging previously c) what do we estimate the long-term level of support for such a party will be and d) won't such a party ultimately find it hard to differentiate itself from its big right-wing brother?