Former Florida Gov. Jeb Bush was forced to defend himself Thursday after left-wing groups attacked him for suggesting that the U.S. "phase out" Medicare.

On Wednesday, the Republican presidential candidate told supporters in New Hampshire that the federal health insurance program for Americans age 65 and older could benefit from a major overhaul.

"We need to make sure we fulfill the commitment to people that have already received the benefits [and] that are receiving the benefits," Bush reportedly said. "But we need to figure out a way to phase out this program for others and move to a new system that allows them to have something, because they're not going to have anything."

Bush later found himself pilloried by liberal groups after his comments were uploaded to YouTube by the Democratic National Committee.

The progressive Agenda Project Action Fund, known for its 2011 advertisement featuring an elderly woman being pushed off a cliff by an actor playing Paul Ryan, circulated an email in which they accused Bush of wanting to terminate a plan "that literally keeps old people from dying."

Erica Payne, AP Action's founder, wrote in the email that Republicans "hate" Medicare and "will not stop until they end Medicare."

"If you want your grandmother to die, vote Republican. If you want your grandfather to die, vote Republican," Payne wrote. "It is less expensive than hiring a hitman."

Payne also hinted at recreating its "Granny Off a Cliff" ad, this time featuring the Republican presidential hopeful.

"Help us bring Granny back so she can roll over Jeb Bush and the Republican plans to destroy Medicare as we know it," she wrote.

According to Politico, the DNC also issued a statement saying that if Bush becomes president, "people who are working hard now, playing by the rules, putting in long hours, and saving for their retirement, won't have the same health benefits that seniors rely on."

Bush first had to defend his comments when an elderly woman at Wednesday's event asked him: "Why are you always attacking seniors?"

The former governor responded by describing Medicare as "an actuarially unsound healthcare system."

He advised against eliminating or making changes to the benefits that individuals who are already enrolled in Medicare are receiving, but said that "your children and grandchildren are not going to get the benefit of this that they believe they're going to get or that you think they're going to get, because the amount of money put in compared to the amount of money the system costs is wrong."

The Florida Republican applauded the medical voucher program that Mitt Romney's running-mate first proposed and which Democrats have previously described as an attempt to "end Medicare as we know it."

Under a voucher system, the government would provide future seniors citizens enrolled in Medicare with a direct payment towards whichever insurance option they choose while also establishing new standards for employer-based retirement plans and the benefits they offer.

Other GOP candidates including New Jersey Gov. Chris Christie and Florida Sen. Marco Rubio have discussed the need for Medicare reform and a re-examination of other entitlement programs.

"If we want to reform these programs in a way that doesn't impact anyone like my mother — people currently in the program or about to retire — it will require my generation and your generation to accept that our Social Security and our Medicare is still going to be the best in the world, but it's going to look different than our parents' Social Security and their Medicare," Rubio said at the Republican Leadership Conference in April.

Bush called the attacks from his liberal opposition "just ridiculous" and criticized their demonization of Republicans looking to offer solutions.

"We need to have a grown-up conversation about these issues," he told reporters.