Two leading Democratic candidates for governor of Maryland harshly criticized the rollout of the state’s online health insurance exchange Thursday but sparred during a candidates forum over the wisdom of a solution one of them proposed earlier in the day.

Attorney General Douglas F. Gansler and Del. Heather R. Mizeur (Montgomery) both told an audience of senior citizens that Maryland had no excuse for botching the start of its exchange, which has been riddled with glitches since its Oct. 1 debut.

“If I were governor, we would never have had this problem to begin with,” Mizeur said at the 90-minute forum hosted by the Democratic club at Leisure World, a large retirement community in Montgomery County.

Gansler called the state’s Web site “a disaster” and touted an idea he announced earlier Thursday: to allow Marylanders the option of purchasing health insurance through the federal exchange or the state exchange. Gansler called it “an easy solution to what was a preventable problem.”

Mizeur, however, said that Gansler’s plan was “irresponsible” and something she had been told the federal government would not permit. By contrast, Mizeur said, she would pursue “thoughtful solutions that will actually fix problems.”

Gansler insisted after the forum that his plan was viable, citing support for the idea from Rep. John K. Delaney (D-Md.). A campaign spokesman added that “there are no clear guidelines” for what action a state can take when its own Web site is “broken.”

Lt. Gov. Anthony G. Brown (D), who was tasked with overseeing the state’s implementation of federal health care reform, planned to participate in Thursday’s forum but was unable to attend.

Shortly before the event began, Brown’s office announced that his 89-year-old father, a doctor who grew up in poverty in Jamaica, had died earlier in the day. In a statement read to the audience, Brown said he had gone to New York a few days ago to be with his family as his father was moved from a hospital to hospice care.

Brown campaign manager Justin Schall declined to respond to what the other two Democrats had said about the health exchange.

“Tonight is not a night for politics for us,” Schall said.

Gansler and Mizeur fielded a wide range of questions from the audience — on issues including gun control, hydraulic fracturing and their choice of running mates — and disagreed outright on very little. Many of their appeals were cast in terms of who was better equipped to implement policies and who was the first to embrace an idea that they and most other Democrats now agree upon.

Gansler, for example, said he was the first gubernatorial candidate to endorse a plan to raise the minimum wage from $7.25 to $10 an hour. Mizeur said she had been involved in the debate over hydraulic fracturing, or “fracking,” long before most people knew about the controversial process of extracting natural gas from the Marcellus Shale.

Both candidates agreed that they would do a better job looking out for Montgomery County if elected governor.

“They think our streets are paved with gold,” said Gansler, a former Montgomery state’s attorney who touted the fact that he would be the first Montgomery resident elected governor of Maryland.

He said the county needs to be treated more fairly in the budget process in Annapolis.

“It’s absolutely unacceptable that we keep giving in and not getting back,” Gansler said.

Mizeur largely agreed that Montgomery would benefit from a governor from the county but said that she and other lawmakers from the area have delivered more than they are often credited for. Mizeur cited major transportation legislation passed last year — an increase in gas taxes — that was needed to keep the planned light-rail Purple Line project on track.

The candidates also addressed the state’s gun control laws, in light of the recent shooting at a shopping mall in Howard County. Gansler ticked off things that he has done to crack down on gun supplies and access in the state, including supporting buy-back programs. He said that there are at least three types of people who are most dangerous armed: those in domestic violence situations, those who are mentally ill and convicted felons.

Mizeur called for universal rules for all gun purchases instead of having different standards for handguns and rifles. That would mean background checks for everyone purchasing a firearm and requiring that purchasers are at least 21, she said. Mizeur also said that more money should be put into gun buy-back programs and that firearms should be removed from any places where police respond to address domestic violence.

“We were all struck, deeply, by the terror that was unleashed in the Mall in Columbia last weekend,” Mizeur said. “That tragedy should serve as a reminder for all of us that this is happening in Baltimore City every day. This isn’t something that we can only care about when it’s happening in suburban shopping malls.”

The most spirited exchange came over the health-care rollout. Maryland is one of 14 states that opted to build and run their own health-insurance marketplaces rather than rely on the federal portal.

Brown and other Maryland officials have acknowledged significant problems with the state-run exchange, but Gov. Martin O’Malley (D) has said repeatedly in recent weeks that the exchange is now functional for most users.

Gansler’s proposal Thursday echoed an alternative that had been previously floated by Delaney. This month, O’Malley’s health secretary wrote Delaney a letter saying that moving Marylanders to the federal health exchange would carry more risk than benefits.