Denver Mayor Mike Johnston’s popularity is holding steady after 11 months in office, according to a new poll released Wednesday, but its findings suggest a sales tax increase he’s pitching for the November ballot could face some skepticism from voters.

Johnston remains confident in his tax proposal, unveiled Monday. It would generate an estimated $100 million a year to expand on the city’s affordable housing work, including by preserving or building tens of thousands of units affordable to people now getting priced out of the city. His own internal polling suggests two-thirds of the city would support the tax increase, he said.

But the June survey of 409 registered Denver voters for the nonprofit Colorado Polling Institute found that a solid majority — 64% — believe the city’s taxes are already high. Among them, 35% said the city’s taxes were “way too high,” while 29% said they were “high but acceptable.”

Still, it’s been rare for Denver voters to turn down tax increases, and a pollster noted that plenty of voters voiced moderate opinions on the question.

Those responses were collected before Johnston announced his proposed 0.5% affordable housing sales tax. If the City Council gives its blessing in the weeks ahead, that new tax would share the November ballot with a new 0.34% sales tax being sought to shore up the finances of Denver Health, the city’s safety net hospital.

If both pass, the city’s effective sales tax rate would increase from 8.81% to 9.65%, making Denver stand out along the Front Range.

The bipartisan poll, conducted by Democratic polling organization Aspect Strategic and Republican firm New Bridge Strategy, was conducted via a mix of online and phone interviews between June 13 and 18. It has a margin of error of 4.85 percentage points.

In good news for the mayor, the poll found 48% of voters viewed him favorably. That’s virtually flat compared to the 46% who viewed Johnston favorably in a Colorado Polling Institute poll in August, just his second month on the job.

But the share viewing Johnston unfavorably climbed significantly, from 22% in August to 38% in June, according to the results.

That’s due in part to rising familiarity as Johnston has been in the news, including as he’s spearheaded a new homeless strategy and responded to the migrant crisis. Just 11% of voters told pollsters they had no opinion or had never heard of the mayor in June, down from 32% in August.

His favorability ratings in the new poll contrast with results from a Magellan Strategies survey of 1,595 Denver voters conducted in May. That poll found that 43% approved of his performance — while fully 50% disapproved. The margin of error was 2.45 percentage points.

The survey was conducted for the council’s central office primarily to gauge support for a potential tightening of term limits. Its contract with Magellan was valued at up to $29,000, council spokesman Robert Austin said. The poll also found that the council’s approval rating was underwater, with approval at 36% and disapproval at 49%.

Regardless of his own support levels, Johnston is banking that voters will approve his tax request in November.

On the Colorado Polling Institute survey’s taxes question, Lori Weigel, of New Bridge Strategy, viewed the responses with some nuance. She noted that just about any voter is liable to say they pay too much in taxes, which is why the poll allowed respondents to grade the city’s tax burden by offering several options: way too high, high but acceptable, about right and lower than what one would expect.

“When we look at the ‘high but acceptable’ or ‘about right’ (responses), it’s a majority sort of gravitating towards that middle spectrum,” Weigel said.

The Johnston administration has done its own polling. In a meeting with Denver Post journalists on Tuesday, the mayor said his data shows 65% of city voters would favor the “Affordable Denver” sales tax increase. That figure was steady regardless of whether respondents owned or rented their homes, he said.

“We were really surprised that you have total alignment between renters and homeowners, and you also have — not surprisingly — massive support from younger voters for this issue,” Johnston said. “As we know, if you can’t afford to live here, then all the rest of the other things are secondary.”

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