It isn't even a bleep in the radar of the issues that voters consider the primary ones this election year.
Most important issues: When asked what they consider are the most important issues, 25% of registered voters cited the economy as the top issue, followed by 24% who cited the war on terrorism as the top issue. The situation in Iraq was rated the top issue by 17% of registered voters, moral values issues such as gay marriage and abortion were the top issue for 16% of respondents, and health care was the most important issue for 11% of respondents. -- Source
I was polled by Zogby recently, and she had to "write it in;" something she claimed that she had done many times that day. Most polls that ask specifically about approval/disapproval re: illegal immigration are very clear.