The last time Ben Houchen ran to be mayor of Tees Valley, a struggling, deindustrialized region in northeastern England, he stormed to victory with almost 73 percent of the vote.

Three years on, Mr. Houchen, a Conservative politician, faces a re-election contest in which even a narrow win would do.

As voters in England prepare to vote in Thursday’s local and mayoral elections, the governing Conservatives, led by Prime Minister Rishi Sunak, are trailing badly in the opinion polls to the opposition Labour Party ahead of a general election expected later this year.

So Mr. Houchen has campaigned on his own achievements, relying on his personal brand as the poster boy for “leveling up” — the Conservatives’ flagship policy of bringing prosperity to disadvantaged regions of England.

But with Britain’s economy stagnating and its health service in crisis, will that be enough to outweigh the backlash facing the broader Conservative Party?

“If Houchen loses, given the profile that he has, and given that in mayoral elections people are more likely to vote for the individual, that would suggest that it is actually his Conservative links that have done for him,” said Paul Swinney, director of policy and research at the Center for Cities, a research institute. “Him losing would be bad news for Rishi Sunak.”

The result in Mr. Houchen’s region could determine not just his fate, but that of the embattled Mr. Sunak. Victory would give the prime minister something positive to talk about on Friday when results come in and the Conservatives expect losses elsewhere. Defeat could stir panic among Tory lawmakers and possibly prompt a push to replace Mr. Sunak.

Leveling Up

Once an area controlled by the left-of-center Labour Party, Tees Valley is part of a swath of England’s formerly industrial North and Midlands where voters switched en masse to the Conservatives in the 2019 general election.

Since Mr. Houchen first became mayor in 2017, a vast, derelict steelworks near the town of Redcar has been demolished and cleared for new projects, a failing airport has been saved and civil servants and filmmakers have been lured far from London to the northeast.

Many people in the area give him credit for these achievements. Heidi McCullagh, 42, runs a sandwich shop and catering business near the historic Transporter Bridge across the River Tees.

“We are 110 percent behind Ben Houchen because he has created so many jobs,” said Ms. McCullagh whose windows display his posters. “We do quite a lot of catering for businesses in the area, it’s definitely picked up,” she said. “Ben Houchen does everything he can to make Tees Valley a better place.”

Not everyone agrees. At the heart of his regeneration plan is an ambitious project called “Teesworks,” where, on the site of the former steelworks, construction vehicles busy themselves on a moonscape-like tract of land.

The idea is to convert this into a hub for low-carbon industries but critics accuse Mr. Houchen of mishandling things to the financial advantage of two businessmen.

The project, which has involved hundreds of millions of pounds in public investment, was initially half publicly owned, but a subsequent deal left the private-sector partners in the venture with 90 percent ownership. (Mr. Houchen declined requests for an interview, but has publicly defended the deal.)

An independent review in January found no evidence of corruption but described “issues of governance and transparency” and said a number of decisions had not met “the standards expected when managing public funds.”

Last week, Steve Gibson, a former collaborator on the project and the chairman of a major soccer club in the area, accused Mr. Houchen of “giving away everything they had worked for,” an intervention that may boost the chances of Labour’s candidate, Chris McEwan.

‘An Emerald City’

On a bitingly cold day last week, five activists hung a banner from a road bridge near Redcar.

“Honk if you want Houchen out,” the banner read, and a steady flow of motorists sounded their horns as the protesters, wearing masks of Mr. Houchen’s face, cheered and waved.

“He promises that Teesside will become an emerald city,” said Ray Casey, a member of a small group that opposes Mr. Houchen, called Teesside Resistance. “It’s always just over the horizon though — we never get there.”

Sipping a beer later, Mr. Casey, 63, said he felt the mayor ran “an operation entirely based on public relations and spin.”

Yet no one disputes that investment has come to a region of 304 square miles with a population of around 660,000 people, or that Mr. Houchen has good contacts. Last year he was nominated for a seat in the House of Lords by his ally Boris Johnson, the former prime minister. He also has ties to Michael Gove, the Conservative minister responsible for “leveling up.”

In the town of Darlington, a shiny modern building is now the northern base of the Treasury, Britain’s finance ministry. Rail stations are being spruced up. A film studio has risen from the site of an old bus depot in Hartlepool, a gritty seaside town a long way from Hollywood in every sense.

The question is how much this is benefiting local communities.

Sacha Bedding, chief executive of the Wharton Trust, a charity based in Hartlepool, said investment was “creating the conditions that will give the area a proper stab” at regeneration, but that little had yet improved in the neighborhood.

“The number of people who have fallen into financial insecurity has grown and people who are working have struggled massively,” said Mr. Bedding, adding that many lacked hope. “When not a lot feels like it has changed you almost end up with the attitude, ‘Well what’s the point in voting?’”

Sitting on a bench in Darlington, Ryan Walton, 19, said he planned to vote Labour. “Things have improved but not enough,” said Mr. Walton. “It would be better if they broadened their horizons and redeveloped areas where people live.”

Green Shoots

In a fractious televised debate last week, Mr. Houchen defended his record against attacks from Labour’s Mr. McEwan and Simon Thorley of the centrist Liberal Democrats.

In a dark suit, white shirt and striped tie, Mr. Houchen was confident and pugnacious, accusing critics of peddling conspiracies.

“If you think you can turn around and change fortunes in just a few short years that just doesn’t happen, but what we are seeing is the green shoots,” Mr. Houchen said when asked whether local people felt better off.

For the film making business, some of those green shoots can be seen in a movie called “Upgraded,” parts of which were filmed at Teesside International Airport, which stood in for a New York airport.

Mr. Houchen brought the loss-making airport into public ownership in 2019, an unusual market intervention for a Conservative politician.

But in terms of its main business — aviation — Teesside International has yet to break even and offers only a handful of flights on most weekdays.

Waiting in a largely deserted departure area before flying to Amsterdam, Derek Muir, 68, praised Mr. Houchen for saving the airport and said he would vote for him because “he gets things done and brings investment into the area.”

Looking around the airport, however, he said that the lack of any flights to London was disappointing. “I would like it to be more busy,” he added.