John McCain may be able to score some points against Barack Obama if his campaign continues to use former Weather Underground member Bill Ayers against the Democratic nominee. But McCain is likely to pay a price, too.

HCD Research and the Muhlenberg College Institute of Public Opinion conducted a study of reactions to a speech Sarah Palin gave in which she invoked Ayers to attack Obama. They came up with some interesting results.

Obama's favorability ratings took a hit after participants viewed a clip of Palin's speech. Before watching the clip, 23 percent said they had a "somewhat favorable" opinion of Obama. Afterward, that number fell to 18 percent. That decline, HCD reports, is statistically significant at an 80 percent confidence level.

McCain also suffered, however. Before they viewed Palin's speech, 25 percent of participants said they had a "very unfavorable" opinion of the Republican nominee. Afterward, that number rose to 31 percent -- again, the uptick was statistically significant at an 80 percent confidence level.