A voter initiative aimed at restricting government services provided to illegal immigrants in Arizona is losing support as uncertainty about it grows, according to a poll released Friday.

Supporters of Proposition 200 (search) still outnumber opponents, 42 percent to 29 percent, but 29 percent said they are undecided, according to the survey by Northern Arizona University's Social Research Laboratory.

The measure, which Arizona voters will decide Nov. 2, would require proof of citizenship to vote and to receive some types of government services. Government workers would face a $750 fine and up to four months in jail for failing to report when people illegally apply for government aid.

A poll released in July by Arizona State University said about three of every four voters surveyed said they supported the initiative.

"(Voters) are taking a second, third and fourth look at it now," said Fred Solop, the laboratory's director and a political science professor.

When state agencies cited the high costs of enforcing the proposal, the public started listening more closely, Solop said.

Supporters of the proposal say illegal immigrants are draining Arizona's coffers by fraudulently obtaining government services. In recent years, illegal immigrants have increasingly flocked to Arizona as the federal government has clamped down on other popular crossing areas in California and Texas.

Opponents say the proposal would do nothing to stop fraud.

The NAU poll of 594 likely voters was conducted Oct. 8-11 for the Arizona Indian Gaming Association (search), which said it has not taken a position on the proposal. The poll had a margin of error of about plus or minus 4 percentage points.