HARRISBURG U.S. Rep. Allyson Y. Schwartz challenged businessman Tom Wolf to disclose details of a $4 million bank loan he obtained for his campaign during a sometimes-tense debate Wednesday among Democratic candidates for governor.

"I'm the only one who has not borrowed or given money to myself," Schwartz said, turning to Wolf in a lecture hall at Widener University Law School's Harrisburg campus. "What did you use for collateral? What are the terms? . . . What does it mean to the taxpayer to have a governor paying millions back to a bank?"

It was a rare pointed moment in a race that has been characterized by broad policy agreement.

"I guess I'm 'it,' " Wolf said. "I do owe an explanation." He said that he got the loan, part of $10 million he has given his own campaign, "using personal assets, not corporate assets" of his building-supply company, adding that self-funding was the only way he could compete as a political neophyte.

"I had an impulse for some popcorn and a beer," joked Katie McGinty, former head of the state Department of Environmental Protection, who stayed out of the fray in the 90-minute debate.

The three candidates met 41 days from the May 20 primary as the Democratic race is heating up. All of the campaigns are now advertising on television and ramping up their voter-turnout operations, entering the phase of the battle in which the party's voters likely are paying the most attention.

Wolf, spending more than all of his rivals combined, has cruised to a lead of better than 25 percentage points as measured by the latest independent poll, from Franklin and Marshall College. Strategists expect the race to tighten.

State Treasurer Rob McCord, the fourth candidate in the race, did not attend Wednesday's debate, citing a long-standing commitment to attend the state AFL-CIO convention in Pittsburgh.

McCord has tried to distinguish himself from the field by proposing a 10 percent tax on drilling of natural gas from the Marcellus Shale, twice as high as his three opponents; it is featured in his latest TV ad.

"Ten percent is not going to pass," McGinty said, adding that a tax has to be "reasonable." Pennsylvania is the only state that produces natural gas that does not impose a severance tax.

Schwartz went on the offensive in her opening statement, saying "being governor is not like running a business," a clear reference to Wolf. Later, she said that her career in Congress and in the state Senate, where she helped to pass the Children's Health Insurance Program in the 1990s, was the best preparation to be governor.

"This is hard work," Schwartz said. "It's not just having a good idea. . . . It takes an almost relentless sense of mission." She said that getting the health program passed required "being persistent" and pushy, willing to "not have everybody like you."

Wolf's personal financial disclosure form listed a loan from M & T Bank at 3.8 percent interest, but candidates are not required to lay out other terms of loans. His campaign said it would make the full loan agreement available as soon as possible.

"Make sure we see those documents," Schwartz reminded near the end of the debate.

Afterward, Wolf spokesman Mark Nicastre said Schwartz "proved that she is a typical politician who is behind in the polls."

"Tom Wolf answered all of her questions because he wants to be a different kind of leader for Pennsylvania," Nicastre said.

A panel of journalists asked the questions in the debate, sponsored by the Pennsylvania Legislative Correspondents Association, Widener Law, and PCN, which televised it live.