Selzer & Company for Bloomberg, 12/4-7, 1,000 adults. MoE 3.1%.
Note that both Hillary Clinton and Barack Obama crush the two top GOP figures, George W. Bush and Sarah Palin, each of whom have net negative favorability ratings in the double digits, Bush by 18 and Palin by 24. The Democratic Party as a whole is +5 while the GOP is -5. The only matchup where the GOP does better on net favorables is Nancy Pelosi vs. John Boehner, but that's just because most Americans have no idea who John Boehner is. Pelosi's positive rating is actually a tiny bit higher than Boehner's.
And last but not least, notice that the tea party basically looks like a slightly less popular version of the Republican Party. It's obviously become an extremely important force within GOP politics, but barely more than a third of the country views it favorably and it's net rating is -4, virtually identical to that of the GOP.
Bottom line? Americans still like Democrats and the Democratic Party more than Republicans and the Republican Party.