Scott Walker, governor of Wisconsin and 2016 Republican presidential candidate, eats a pork chop at the Iowa Pork Producers Association booth during the Iowa State Fair in Des Moines. (Daniel Acker/Bloomberg News)

Most Republicans like Scott Walker. He seems like the kind of guy who could live down the street — a middle-aged Midwestern dad who never finished college, rides a used Harley and brags about the deals he gets at Kohl’s department store.

But few Republicans want him in the White House. Perhaps by trying so hard to convince voters that he’s just like them, Walker has stopped looking presidential.

His collapse in the polls — plummeting to 2 percent nationally in a new Washington Post-ABC News survey — has made the second Republican debate Wednesday a crucial moment for the Wisconsin governor, providing him with an opportunity to show voters he has the gravitas to lead the country.

But the venue also holds great risks for Walker, who has never done particularly well in debates and often struggles when confronting rivals in person. He has promised a more passionate performance than he gave in the first GOP debate, when he described himself as “aggressively normal” and mostly faded into the background.

“We want to lay out some contrast,” Walker told reporters last week in Illinois. But he added: “We’re certainly not going to go into personal attacks.”

Republican presidential candidate Wisconsin Gov. Scott Walker speaks during a town hall meeting in Las Vegas. (Isaac Brekken/AP)

Prominent supporters have grown increasingly alarmed by Walker’s plunging poll numbers and uneven performance on the campaign trail. If he doesn’t do well in the debate, donations could dry up, several of his prominent supporters said. They also warn that he could be in danger of not making the stage in future debates if he doesn’t turn things around soon.

“He has to do well in the debate — he just has to,” said one donor, who spoke on the condition of anonymity for fear of upsetting the campaign. “He’s got to have a good debate. Period.”

It has been a rapid fall from just two months ago, when Walker formally entered the race near the top of the polls and promised a different kind of campaign — the everyman candidate.

Known for wearing a suit to class in college, Walker didn’t put on a tie or blazer when he made his July announcement. He switched from private chartered planes to commercial flights and memorized his speeches so he didn’t have to use notes. He shared pictures of the greasy food he ate.

During his first week as a candidate, Walker’s top campaign workers and family tagged along for a whirlwind tour of five states, tweeting photos of the governor pulling his own suitcase, pumping gas and drinking Coors Light. Walker talked about shopping at Kohl’s, hitting the sales racks and using coupons to get deals.

“And next thing you know, they’re paying me to buy the shirt!” he marveled at stop after stop. (Late-night talk-show host Jimmy Fallon quipped, “Maybe he can go to Kohl’s and buy some new material.”)

U.S. Republican presidential candidate and Wisconsin Gov. Scott Walker removes his helmet after arriving at the Salem-Derry Elk’s Lodge in Salem, N.H. (Mary Schwalm/Reuters)

Donors gushed that Walker seemed more interested in getting to know them than asking for a check. After a series of presidential nominees who struggled to connect with voters, Walker seemed like the GOP’s answer. Early polling backed up his potential.

“Too many of our presidents went to Hah’vard and Princeton,” said Mary Stimek, 63, who met Walker during a breakfast meet-and-greet at a barbecue joint in Nashville in late July. “People are tired of that East Coast elite. He relates to the common person.”

But no one predicted the rise of Donald Trump, a billionaire from a wealthy New York family who travels on a private jet and dislikes shaking hands with germ-ridden supporters. While other candidates tried to relate to average voters at the Iowa State Fair, Trump wore white shoes, refused to have more than one bite of a greasy pork chop (Walker ate two) and took children for rides in his helicopter.

Trump’s gaudy brand of authenticity has outshone Walker’s regular-guy routine. The billionaire is also benefiting from voter anger at career politicians — a vulnerability for Walker, who has been campaigning for office since he was 22.

“A career politician, in my mind, is somebody who has been in Congress for 25 years,” Walker said in a recent CNBC interview, calling himself a “public servant.”

The first GOP debate Aug. 6 is considered the moment when things really began to fall apart for Walker. One of 10 candidates on the stage, he did not stand out. His answers were workmanlike and lackluster, and he often did not fill his allotted time.

The goal was to be the nice guy on stage, one who diplomatically stays above the fray. Instead, many forgot he was there. Ever since, Walker’s poll results have been in free fall.

His aides note, however, that he has retained high favorability ratings. A recent survey by Quinnipiac University found that 62 percent of likely Republican caucusgoers in Iowa still like Walker, even though only 3 percent say they would vote for him. Supporters say this shows he still has an opportunity to rebound with voters.

Soon after the debate, Walker began targeting Trump’s supporters by embracing controversial positions and bashing Republicans in Washington and back home in Wisconsin. His social media accounts became more polished — no more photos of fast food or his treadmill screen — and he now regularly wears a suit and tie. He even experimented with a teleprompter during a foreign policy speech.

Walker no longer talks about Kohl’s. Instead, he promises to “wreak havoc on Washington,” a phrase that strikes some supporters as out of character for the mellow governor. Walker won’t say where the new wording came from.

“It’s just something out there,” he told reporters last week. “People want somebody to shake it up, and another way to phrase it is to ‘wreak havoc on Washington.’ ”

Walker also is doubling down on the issue that lifted him to national prominence in the first place: attacking unions. On Monday in Las Vegas, he laid out a plan to dramatically weaken unions nationwide by eliminating a federal labor board, forbidding unions for federal employees and passing national right-to-work legislation, among other things.

After long refusing to attack his opponents, his campaign released a Web video criticizing former Florida governor Jeb Bush for not promising that he would rip up the Iran deal on his first day in office. Walker has criticized senators for not repealing the Affordable Care Act and fellow governors who expanded Medicaid. Walker told reporters that he plans to continue pointing out differences during the debate Wednesday night.

The everyman side still emerges here and there. Over Labor Day weekend, Walker rode a rented Harley-Davidson Road King through New Hampshire’s 10 counties wearing faded jeans, a T-shirt and fingerless leather gloves.

“You look just like one of us,” Bob Healey, 68, marveled when Walker stopped at his breakfast table at Munroe’s Family Restaurant in Twin Mountain.

Walker grinned: “That’s a good thing, right?”