Tom Harris doesn't much care for the Liberal Democrats:
Having seen the damage done to the Labour Party through its association with the Liberals in the Scottish Parliament in previous years, there is, if anything, more hostility among MPs to the idea of power sharing than ever.
On the other hand, if the Liberal Party want to sign up to the implementation of Labour’s manifesto in the aftermath of the election, fine. So long as they don’t expect either Labour or Tory MPs to agree to a change in the electoral system so that every possible outcome in future would result in the Liberals being in government.
Now I'm as fond of Lib-Dem bashing as the next fellow, but is it really true that Labour lost the last Scottish election because it had been hamstrung by its junior coalition partner? I think not. The Lib Dems may not be up to much; then again nor is the Scottish Labour party. The electorate wearied of them. The'd had eight years in power, after all. Equally it was Labour's insistence that any vote for the opposition was, in the case of the Tories "anti-Scottish" and, in the matter of the nationalists "anti-British" that helped confirm the view that, rather than argue matters on the merits, the Labour party felt it had a divine right to permanent rule. Thankfully just enough people demurred from that view to give the party an entirely-deserved kicking. And it was not as if the Labour-Liberal coalition had been a soaraway success, anyway. But if Labour think it was all the Lib Dems' fault then they're still in a state of some denial.
Equally, while there are plenty of good arguments for sticking with the current electoral system at Westminster, it's not the case that changing it would guarantee the Liberals a permanent presence in government (though if it did and that presence were to moderate the worst excesses of either other party then that would not necessarily be a terrible outcome. That's a mighty and unlikely "if" of course). After all, a change in the electoral system might change the make-up of parliament too. Rather than three (or, if you prefer, two and a ahlf) parties plus an assortment of nationalists, you might eventually have half a dozen major parties (or constitutencies, if you like) represented at Westminster. That would lead us into very different territory and a very different politics. But it's not the case that "voting reform" would necessarily give the Liberals a permanent ticket to government.