The Salt Lake Tribune survey shows Corroon at 39.8 percent compared with Ivory's 32.6 percent. Undecided voters are outpolling Cook, 15.2 percent to 11.5 percent.

Valley Research surveyed 654 registered county voters who said they planned to cast ballots. The poll - conducted Oct. 21 through 26 - carries a 3.8 percent margin of error.

The poll numbers do not reflect the court battle over Ivory's name being on the ballot. Respondents were simply asked: "If the election were held today, for whom would you vote for Salt Lake County mayor: Peter Corroon, Democrat; Ellis Ivory, Republican; Merrill Cook, independent."

Corroon said Thursday afternoon that his campaign was taking nothing for granted.

"With 15 percent undecided, this race is too close to call," he said.

Ivory - bolstered by Thursday's court decision placing his name on the ballot - said he was "heartened" by the poll numbers that put him within striking distance of Corroon.

"The good part is that we know we have a lot of work to do," Ivory said. "We will be invigorated by the challenge of these polls numbers."

Even so, former two-term Republican Congressman Merrill Cook could siphon enough GOP votes from Ivory to land Corroon in the winner's circle.

The Tribune survey contains data for party affiliation and religious preference that could give Corroon an edge, said Tim Chambless, professor of political science at the University of Utah.

The poll shows Corroon getting 77 percent of the Democratic vote, with Ivory snaring 58 percent of Republican respondents.

"That tells me that the Republican Party is fragmented by Cook and those who would have voted for Mayor Nancy Workman," Chambless said.

The poll also shows Ivory, who is active in the LDS Church, capturing 45 percent of the Mormon vote compared with 24 percent of the LDS vote for Corroon, a practicing Catholic.

"For Corroon to take one-fourth of the LDS vote means other factors have entered in," Chambless said. "He's passed the litmus test. He's a family man with a business background. He's seen as an acceptable Democrat."

But Chambless noted that - with this year's strong GOP ticket - many Utahns will vote straight Republican, boosting Ivory's chances.

The latest poll also shows voters overwhelmingly favor renewing the Zoo, Arts & Parks (ZAP) sales tax.

csmart@sltrib.com