Mayor Sylvester Turner retains a wide lead over his opponents, most of whom have failed to gain traction with weeks left until Election Day, according to a University of Houston poll released Sunday.

The poll, published on the eve of early voting, shows Turner with 43.5 percent support among likely voters, followed by lawyer and businessman Tony Buzbee at 23.4 percent. Bill King, Turner’s 2015 runoff opponent, trails with 7.8 percent, while 6.8 percent of voters said they support Councilman Dwight Boykins.

Former councilwoman Sue Lovell was backed by 1.2 percent of respondents, while 0.2 percent of voters said they support one of the other seven candidates. Another 17.2 percent of likely voters said they remain undecided.

For the poll, 501 likely voters were surveyed between Oct. 1 and Oct. 9. The margin of error is 4.4 percent.

Released weeks after a prior survey found Turner leading with 37 percent support, the new survey shows the mayor inching closer to the 50 percent-plus-one vote he would need to win the Nov. 5 election. If no candidate receives a majority of votes, the election will head to a December runoff between the top two finishers.

A significant share of undecided voters said they are considering Turner or view him favorably, results that indicate he has a narrow but unlikely path to outright victory on Nov. 5.

“Anything’s possible,” said Renée Cross, senior director of the Hobby School of Public Affairs and co-director of the poll. “Prior to this poll, I would have put my money on a runoff. But if you look at the undecided voters, there’s a possibility he could squeak it out in the general.”

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The results show Turner maintains strong support among the base of progressive and African-American voters that boosted him into the mayor’s office four years ago. He captured 59 percent support from black voters, compared to Boykins’ 14 percent share. Every other candidate was below 5 percent among black voters, with 19 percent undecided.

Meanwhile, 63 percent of Democrats said they back Turner, while no other candidate broke double digits. Buzbee received 56 percent support among Republicans, far ahead of King, who was supported by 16 percent of Republicans, his core base of support in 2015. Another 12 percent of Republicans back Turner.

“King and Buzbee are in many ways fishing in the same pond, and Buzbee is catching far more fish than King is,” said Mark Jones, a Rice University political science professor who co-directed the poll.

Respondents largely expressed distaste for President Trump, with 63 percent saying they have an unfavorable view of the president, compared to 32 percent favorable. Eighty-five percent of Turner’s supporters view the president unfavorably, the poll found, while 80 percent of Buzbee voters support Trump.

The results indicate Turner would be well-advised to continue running ads that bring up Buzbee’s previous ties to Trump, Cross and Jones said.

“What gets Democrats energized? It’s not always great Democratic candidates. Sometimes it’s a candidate on the other side of the aisle they don’t like,” Cross said. “Good or bad, Trump energizes Democrats and Republicans. But in the city of Houston, Democrats outnumber Republicans.”

King and Boykins are both hampered by low name recognition among likely voters, the poll also found. Though more voters said they view King and Boykins favorably than negatively, 54 percent said they did not have enough information about King, while 69 percent said the same about Boykins.

Those results indicate King and Boykins have room to improve their positions before Nov. 5, Jones said, adding that Boykins could make it difficult for Turner to win without a runoff if he gains in the polls.

“If you’re Turner, you’re more worried about Boykins rising,” Jones said. “More than two thirds don’t know about Boykins, but once people form an opinion of him, more people have a favorable opinion of him than unfavorable.”

Turner is viewed favorably by 56 percent of voters, compared to 36 percent unfavorable and 8 percent who said they do not know enough. Thirty-two percent of voters said they have a favorable view of Buzbee, compared to 39 percent unfavorable and 29 percent who said they do not have enough information.

In a potential runoff, Buzbee could pick up support from King voters, 58 percent of whom listed Buzbee as their second choice. Half of Boykins’ supporters said they view Turner as the next best option.

Still, the mayor maintains a wide edge in each hypothetical runoff matchup, the poll found, with 55 percent of voters saying they would support Turner in a runoff against Buzbee and 36 percent backing Buzbee. Turner also would beat King in a runoff, 55 percent to 32 percent, the poll found.

About one fifth of undecided voters who expressed a preference in at least one candidate said they are choosing between Boykins and Turner, the survey found, with another 16 percent conflicted over whether to support Buzbee or Turner. About 14 percent said they are deciding between Buzbee and King, while 18 percent are leaning toward Turner alone.

Otherwise, 41 percent of those surveyed ranked flooding as the most important problem facing Houston, compared to 22 percent who listed crime as the top issue.

Rising property taxes, traffic congestion and road quality were the top concern of between 8 and 9 percent of voters, while 4 percent or fewer named inequality, air quality and trash collection as the most important problem.

Early voting starts Monday and runs through Nov. 1. Election Day is Nov. 5.

jasper.scherer@chron.com