The Lib Dem 'Mansion Tax' policy could hardly have been presented more ineptly. The person who announced it hadn't told his colleagues about it, and wasn't able to answer simple questions about how it would actually work.
Furthermore, as with any policy which attempts to get rich people to pay more tax, there was a lot of very hostile coverage by the rich people who own and write in newspapers.
And yet for all that, I am willing to bet that if an opinion pollster asked people "Do you support or oppose a 'Mansion Tax' on homes worth over £1 million?" then a majority would support it, and if you asked "Do you think the government should introduce a new tax on homes worth over £1 million to pay for income tax cuts for lower and middle earners?" then an even bigger majority would support it.
Maybe one of those newspapers which has been telling us what an electoral disaster the policy would be will commission a poll and we could find out.