Former Massachusetts Gov. William Weld William (Bill) WeldRalph Gants, chief justice of Massachusetts supreme court, dies at 65 The Hill's Campaign Report: Biden visits Kenosha | Trump's double-voting suggestion draws fire | Facebook clamps down on election ads Biden picks up endorsements from nearly 100 Republicans MORE (R) warned in an interview that aired Monday on "Rising" that millennials will have to pay the price for what he said was President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE's lack of action on the growing deficit and climate change.

"We've had 2 1/2 years almost to see what he does, and I, for one, don't think it's a pretty picture," Weld, who is the only GOP challenger to Trump in the 2020 presidential primary so far, told Hill.TV hosts Saagar Enjeti and Krystal Ball last week.

"Part of what's not pretty is that the president has seen spending go up, or gone right along with spending going up, to the tune of a trillion-dollar deficit every year," Weld said. "His most recent budget added $7.9 trillion to the deficit. Admittedly, it was a multiyear budget, but it gets us up to $30 trillion of deficit."

"I think that raises a big issue of fairness because you know who's going to pay for that? The millennials, you guys," he added. "My generation's not going to pay for that, and the burden is going to fall on you all."

Weld also pointed to the issue of climate change.

"The burden of climate change is going to fall on you all if nothing is done, and [those are] two of the major reasons I'm running," he said.

Weld has repeatedly hammered Trump since announcing his long-shot bid last month.

A Monmouth University survey conducted last month found that only 8 percent of Republicans and Republican-leaning independents would vote for Weld over Trump.

— Julia Manchester