"There's no way to absorb 100,000 to 140,000 more students without building new facilities," said Walt Rulffes, superintendent of the Clark County School District.

But Brad Coker, managing partner for Mason-Dixon Polling & Research Inc., predicted "that the proponents face an uphill battle."

Forty-five percent of Clark County voters said they would be in favor of the measure in November, but successful referendums usually have wider margins of support at the beginning of a campaign, and their support tends to dwindle over time, Coker said.

Thirty-eight percent said they would vote against the proposal, and 17 percent were undecided.

Whenever taxes are involved, opponents have an easier time defeating them, Coker said.

Plus, the Clark County School Board is asking for the public to approve the $7 billion in new bonds during an economic downturn.

"When you deal with a number that big, it scares people," he said.

The pollster also thought it was telling that support was tepid even among Democrats, who were 47 percent in favor of the school construction bonds. Republicans were split, 42 percent in favor versus 42 percent against.

The poll of 405 Clark County residents, commissioned by the Review-Journal and reviewjournal.com, had a margin of error of plus or minus 5 percentage points. The poll numbers have not changed much since the last poll by Mason & Dixon in December.

To be fair, Coker noted the campaign for the bond measure has not started. The Las Vegas Chamber of Commerce came out in favor of the bonds last week, but campaigning is not expected to start until August.

Joyce Haldeman, the district's associate superintendent for community and government relations, said, "The fact that we got half of the support of the people without doing any campaigning to me is a good sign."

Historically, the district's bond issues have had the support of voters.

The last 10-year bond, in 1998, passed by a 65-percent-to-35-percent margin. The construction program was proposed at $3.5 billion at the time, but money created by growth in property taxes and other revenues generated $4.9 billion and paid for 101 new schools and 244 rehabilitation projects.

Because it exceeded its original 1998 goal of building 88 new schools, the Las Vegas Chamber of Commerce sees the district's past record of performance as reason to support the new bond initiative, said Cara Roberts, the chamber's vice president of public relations.

But skeptics such as Andy Matthews, the vice president of the Nevada Policy Research Institute, would like to see the district move away from a "monopolistic model" of education and move to alternatives such as charter schools and school vouchers, which he thinks would be more cost-effective.

School officials said a new 10-year construction plan is needed to extend the 1998 construction program, which will expire this year.

It would pay for 53 new elementary schools, 16 middle schools and four high schools plus site acquisitions and remodeling. The bonds would be supplemented by $2.5 billion in revenue from a hotel room tax and real estate transfer taxes.

The district is asking voters to keep its share of the property tax rate at the current $0.5534 per $100 of assessed value.

For owners of a $300,000 home, approval of the question would mean that they would continue to pay $581.07 annually for school construction.

That amount would fluctuate as a property's assessed valuation rises or falls during the time the bond is in effect.

Rulffes stressed that the bonds would be earmarked for construction. The money could not be used for operating expenses like salaries.

"I believe once people better understand the issue, they support it," Rulffes said.

Contact reporter James Haug at jhaug@reviewjournal.com or 702-383-4686.