I like Alan Grayson and his politics but I believe the data support the view that he under-performed relative to other Democratic incumbents in the 2010 elections.
I quickly tabulated the Table below (I hope I didn't make any mistakes) with the Congressional Democratic percentages in 2008, 2010, the Obama 2008 election percentages (Columns A, B, and C, respectively) and the comparison between Congressional 2010 and Obama 2008 (Column D).
The bold districts were Democratic in 2008 and won by the Republicans in 2010. Grayson's district is Florida 8, where the difference relative to Obama was -14 significantly worse than for other Democratic incumbents. The first five districts in the Table were retained by Democrats. I did not include those districts were there was not both a Republican and a Democratic candidate in 2010.
Note that Republican incumbents did quite well in 2010, even in Districts won by Obama Districts# 18 and 10.
So my conclusion is that while Grayson would have lost in 2010 no matter what his position, his strong liberal stands hurt his voting percentage.
Comparison of Congressional Democratic Votes in 2010 to Obama 2008 Vote in Percentages, Ranked by 2008 Congressional Votes.
A B C D
Congressional Vote Obama 2010 -
District 2008 2010 2008 Obama
3 100 63 71 -8
23 82 79 83 -4
20 77 60 63 -3
11 72 60 66 -6
19 66 63 65 -2
2 62 41 45 -4
24 57 40 49 -9
22 55 46 52 -6
8 52 38 52 -14
25 47 42 49 -7
12 43 41 49 -8
15 42 35 48 -13
18 42 33 51 -18
16 40 33 47 -14
5 39 33 43 -10
9 39 29 47 -18
10 39 34 52 -18
13 38 31 47 -16
7 36 31 46 -15
14 25 27 42 -15