A new poll shows the Chargers stadium ballot measure headed for near-certain defeat as many previously undecided voters have begun to oppose the initiative.

A Union-Tribune/10News poll released Thursday shows that Measure C is trailing 55 percent to 45 percent among actual voters and likely voters who are certain how they will vote, down from a 52 percent to 48 percent margin against the measure in mid-October.

The latest poll, which included likely voters and people who have actually cast mail ballots, shows Measure C is far short of the two-thirds support — 66.7 percent — required for approval.

It also shows the measure appears likely to fall short of a simple majority.


That could matter if the state Supreme Court upholds a March lower court ruling that tax increases by citizen’s initiative require approval by a simple majority instead of two-thirds of voters.

Attorneys for the Chargers requested permission this week to file an amicus brief in support of having the Supreme Court make such a ruling.

Getting support from more than 50 percent of San Diegans could also boost the leverage of the Chargers in future negotiations with the NFL and the city on another stadium solution.

The number of undecided voters shrank from 18 percent to 12 percent when the latest poll is compared to the mid-October poll, and it appears a large majority of those making a decision since then have chosen not to support Measure C.


That drop in support comes despite the Chargers spending millions of dollars on TV and radio ads, aggressively soliciting votes on social media and running a strong ground campaign with hundreds of volunteers visiting voters door to door.

The poll, conducted by SurveyUSA, indicated reasons for opposition continue to be doubt the measure would boost the local economy and concerns that it could hurt local tourism.

Another clear trend has emerged regarding ideology and party affiliation, with conservatives and Republicans much more likely to support the measure than liberals and Democrats.

Measure C would increase San Diego’s hotel taxes from 12.5 percent to 16.5 percent to help pay for a combined downtown stadium and convention center annex next to Petco Park.


The poll also showed slipping support for Measure D, a separate ballot measure that would raise the hotel tax to 15.5 percent to possibly fund a convention center annex that could potentially be combined with a privately financed football stadium.

Among voters who have already voted or are certain how they will vote, Measure D is trailing by the same 55 percent to 45 percent as Measure C.

That’s a big drop from the mid-October poll, when Measure D led by a margin of 52 percent to 48 percent among likely or actual voters. And a poll in early October showed voters supporting Measure D by a margin of 55 to 45 percent, so there has been a steady drop.

Getting approval from at least 50 percent of voters is crucial for Measure D, because supporters of that initiative disagree with City Attorney Jan Goldsmith that it needs support from two-thirds of voters for approval, contending that only a simple majority is needed.


Both measures fared worse among those who have already voted than those who haven’t voted but said they were certain to cast a ballot by Nov. 8.

Among those who have already voted, Measure C trailed 54 percent to 42 percent, with the remaining 4 percent choosing not to vote on the measure.

Of those who haven’t yet voted, 39 percent support Measure C while 43 percent oppose it and 18 percent remain undecided.

Among voters who have already returned a ballot, Measure D trails 48 percent to 40 percent. Those who haven’t yet voted oppose Measure D 35 percent to 30 percent, with 35 percent still undecided.


The new poll surveyed 604 likely voters Monday through Wednesday over land lines, smartphones, tablets and other electronic devices and has a margin of error of 4.1 percentage points.

On Measure C, the self-described ideology of those polled had a significant effect on their support.

Those describing themselves as “very liberal” oppose the measure at a rate of 66 percent to 34 percent, while “somewhat liberal” voters oppose it 58 percent to 42 percent and “moderates” oppose it 55 percent to 45 percent.

Voters describing themselves as “somewhat conservative” support Measure C at a rate of 56 percent to 44 percent, while “very conservative” voters support it by 51 percent to 49 percent.


Those number are predictably mirrored in party affiliation, with self-described Democrats opposing the measure 55 percent to 45 percent and self-described Republicans supporting it 51 percent to 49 percent.

Those describing themselves as “independent” oppose the measure at a rate of 57 percent to 43 percent. Independents who say they lean Democratic oppose the measure 66 percent to 34 percent, while independents who say they lean Republican oppose it 61 percent to 39 percent.

The ideology breaks down differently for Measure D, which was written by a group of community leaders and environmental groups.

Very liberal voters are split evenly on Measure D while somewhat liberal voters oppose it by the small margin of 51 percent to 49 percent. Very conservative voters oppose Measure D 65 percent to 35 percent, while the somewhat conservative oppose it 51 percent to 49 percent.


Moderates oppose Measure D 59 percent to 41 percent.

Many voters remain confused by Measure D, which has multiple elements including plans to make the Qualcomm Stadium site a river park and higher education campus if a new stadium is built downtown.

The number of undecided voters on Measure D was 26 percent in the new poll, more than double the 12 percent of voters undecided about Measure C.

However, 26 percent is actually a sharp drop from the 43 percent of voters who were undecided about Measure D in the mid-October poll. Those undecided about Measure C was 18 percent in mid-October.


Decaying support for Measure D could be related to the local hotel industry’s efforts to defeat it with more than $100,000 in radio ads and other efforts since Oct. 24.

Meanwhile, supporters of Measure D haven’t run a robust campaign because they have limited resources after spending more than expected gathering signatures to put the measure on the ballot.

Measure C also continues to suffer from voter skepticism that San Diego would get an economic boost from a downtown stadium and convention center annex.

Of those against Measure C, 77 percent say it would cost the city money and only 4 percent say it would bring the city additional money. Of those in support, 71 percent say it would bring the city additional money and only 10 percent say it will cost the city.


The poll also shows that support for Measure C is lower among whites than other ethnic groups and is supported far less by older voters than younger ones.

In addition, middle-income voters support Measure C more than the wealthy or those with relatively low incomes.

david.garrick@sduniontribune.com (619) 269-8906 Twitter:@UTDavidGarrick