One poll late last month found Wolf with as much as 40 percent of the vote in a field of six.
And now it's a field of five.
John Hanger, a former state environmental secretary, said as he dropped out of the race Thursday that Wolf's ascendancy had made it impossible for him to raise money.
"Tom Wolf has taken this race by the neck," Hanger said. "We have no path to victory."
With about two months until the May 20 primary, some Democrats are echoing Hanger: Can anyone stop Wolf? Last week, he also received the endorsement of Allegheny County Executive Rich Fitzgerald, Pittsburgh Mayor Bill Peduto, and a host of other western leaders.
Katie McGinty, an environmental official in the Clinton White House and later secretary of the state Department of Environmental Protection, began airing TV spots Feb. 24 in the Pittsburgh, Scranton, Harrisburg, and Johnstown markets. She has spent an estimated $500,000.
But U.S. Rep. Allyson Y. Schwartz, who was the front-runner for months, and state Treasurer Rob McCord, have not made a TV play. (Both are from Montgomery County.) Strategists have puzzled over their inaction, noting that McCord reported having $6 million on hand at the beginning of the year, and Schwartz reported $4.6 million.
As time goes on, responding gets trickier, said Democratic consultant Dan Fee, president of the Echo Group in Philadelphia. "People will not only have to introduce themselves, but explain why Tom Wolf is not the right choice," Fee said. "That's tough to do in a limited amount of time."
Schwartz, a five-term representative and a state lawmaker before that, has a base in voter-rich Southeastern Pennsylvania and has been spending money building an extensive voter-turnout operation.
McCord has collected labor endorsements across the state, including from the Pennsylvania State Education Association, the largest teachers' union; AFSCME; and several large Teamsters locals. He also has backing from county party officials outside Philadelphia and Pittsburgh. That institutional support can help turn out votes.
Former Auditor General Jack Wagner of Pittsburgh, also running in the primary, has no television presence and little money, according to the most recent campaign reports.
Strategists looking at the race say it's an open question whether Wolf will have an extensive enough ground operation to help solidify his support and scoop up votes.
The independent public polls so far have shown he leads among registered Democrats, but primary turnout is usually a smaller subset of the party faithful. Organization helps.
"Sure, unions and political folks matter, but you can't be 20 points down going into primary day and have them make the difference," said pollster Terry Madonna of Franklin and Marshall College.
Wolf, who has given his own campaign $10 million, has built his family's company into the one of the largest distributors of kitchen cabinets in the nation. He also served as state revenue secretary in the Rendell administration.
His commercials have introduced him as a former Peace Corps volunteer who lives in the small town where he grew up, earned a doctorate from MIT, shares 20 percent to 30 percent of profits with workers at the Wolf Organization, and drives an old Jeep instead of a luxury vehicle.
All of that sends the message that Wolf would be a "different kind of governor" who would create jobs and increase state spending on education, paid for with a production tax on natural gas.
"Those weren't props. I wasn't faking it," Wolf, 65, said. "I think there's a mistrust of politics as usual, and people are looking for a change."
Tom Thompson, owner of the Mary Ann Donut Kitchen in Allentown, was sold.
"So far, I'm happy that every one of your commercials has been positive," Thompson told Wolf. "You haven't even bashed Corbett yet, and you got your daughters in there, which was a good move."
With front-runner status has come some scrutiny.
Wolf has faced questions for serving as campaign chairman for former York Mayor Charlie Robertson, who was accused of shouting, "White power!" and providing ammunition to a white gang during the city's 1969 race riots, in which a black woman was killed. Robertson was tried for murder but acquitted.
Wolf said that he backed Robertson because of his redevelopment of the city and that he released a video statement from the current mayor, Kim Bracey, who is African American, who praised him as her mentor.
Rivals have also tried to attack Wolf for organizing a legal defense fund for former State Rep. Steve Stetler (D., York), who was convicted on corruption charges for directing employees to perform political work on state time. Wolf and other Democrats have said he was innocent.
Wolf's media approach is familiar to veteran Democratic strategist Neil Oxman.
In the 2002 Democratic primary, he was advising Ed Rendell, who was running for governor against Bob Casey Jr., now U.S. senator and at the time the state auditor. Casey had massive union and state-party support, but Rendell bombarded the TV airwaves with ads for three weeks, unanswered.
Internal polls before the ads showed Casey leading by 17 percentage points. After, Rendell was up by 7 points, Oxman said.
"Then he threw negatives at us. We were able to rebut and make it a referendum on who had the experience to be governor," Oxman said. "He had to try 70-yard passes downfield in May and couldn't come back."
The McCord and Schwartz campaigns, believing Wolf's support has not solidified, hope the result resembles a different Oxman campaign. In 2007, a wealthy businessman who self-financed his campaign, Tom Knox, was leading the Philadelphia mayor's race with 32 percent of the vote.
Knox plateaued while Oxman's candidate, a guy named Michael Nutter, rose in the last three weeks of the primary to win.