Allies to Joe Biden have suggested to the former vice president’s 2020 presidential campaign that he scale back his schedule to limit his gaffes.

The allies have become increasing uneasy about the candidate’s gaffes, the Hill reported Thursday. They said Biden, 76, tends to make the flubs later in the day during longer campaign swings. They have floated giving the candidate more down time as the race for the Democratic nomination is set to heat up in the coming months.

“A lot of people are nervous that he’s lost some of his mojo,” said one major Democratic donor. “They’re getting nervous about him going toe to toe with Trump. But the problem is, there doesn’t seem to be an alternative.”

[Also read: 'He keeps saying stupid stuff': Iowa Democrats concerned about Biden's gaffes]

Democratic strategist Basil Smikle, who is the former executive director of the New York state Democratic Party, said Biden’s stumbles could push voters on-the-fence about him toward other candidates.

One ally, who has spoken with members of the campaign, said Biden “needs to be a strong force on the campaign trail but he also has to pace himself.”

The concerns come after Biden was criticized for not having as full of a schedule as his rivals earlier on in the campaign. They also follow a string of gaffes Biden made in the last week.

For example, he mistakenly said he met with Parkland, Florida, students when he was vice president, but the mass shooting at Marjory Stoneman Douglas High School happened more than a year after he was out of office.

Biden also told Asian and Hispanic voters that “poor kids are just as bright and just as talented as white kids.” He said shortly after that he meant to say “wealthy kids” instead of “white kids.”

In another fumble, he said, “We choose science over fiction. We choose truth over facts.”

Biden’s campaign said the gaffes show the candidate is authentic.

“Joe Biden has spoken his mind his entire life, which voters know and love about him,” said Kate Bedingfield, Biden’s deputy campaign manager. “He’s a real person, he’s authentic, and that will never change. He’s going to keep taking on Trump and making the case to voters about the stakes we face in this election, regardless of how the press chooses to cover him.”