HCD got 554 self-described Democrats and independents to view the ad online, asking them some questions before and after the viewing.
According to the study, 33% of respondents favored Clinton prior to watching the ad, while 35% did so afterward. But the ad helped Sen. Barack Obama (D-Ill.) a little, as well. While 36% said beforehand that they supported Obama, 37% said so after watching it.
And the ad actually made a handful of Clinton supporters move to the Obama camp, with the 100% likely to vote for Clinton slipping to 98%, although it also had its desired affect on 3% of the Obama voters, with 97% of his supporters saying they were still inclined to vote for him.
Among undecided voters, 7% said the ad made them more likely to vote for Clinton, while 5% said it pushed them toward Obama.
There was no word on how Clinton's appearance on Saturday Night Live might have moved the needle.
Clinton and Obama face a crucial set of primaries Tuesday, including Texas and Ohio, which could be make-or-break for Clinton and a momentum-breaker for Obama if one or both go Clinton's way.