In April 2009, Huckabee posted a +8 favorable rating in a PPP poll, with 42% of voters nationwide holding a favorable opinion of him, versus 34% who had an unfavorable opinion. In PPP's latest poll, Huckabee had a -7 favorable rating.
Over that same span, Romney went from a +5 to a -12 (40/35 to 32/44), Palin dropped from -7 to -22 (42/49 to 35/57) and Gingrich fell from -8 to -31 (36/44 to 26/57.)
The fact that the more Americans are exposed to them, the less they like them certainly does not bode well for their competitiveness next year.
The TPM Poll Average shows the same trend, with the net favorability of each potential candidate shrinking.