President Joe Biden narrowly leads former president Donald Trump even though an overwhelming majority of voters are worried about his age, a new Quinnipiac University poll showed.

The poll, conducted from Feb. 15 to Feb. 19, found that 49 percent of registered voters support Biden and 45 percent back Trump in a hypothetical general election matchup.

However, 67 percent of voters said the 81-year-old president is too old to effectively serve another term — compared with 57 percent who said the same of Trump, who is 77. Only 34 percent said Biden had the mental fitness to serve a second term, while 48 percent believed Trump is mentally fit.

Age has become an increasingly prominent issue in both the GOP and Democratic presidential primaries. Trump’s primary opponent, former U.N. ambassador Nikki Haley, has taken swipes at both men over their age and Democratic Rep. Dean Phillips launched his challenge to Biden largely over his concerns that Biden’s age rendered him unfit to run — and win — against the former president.

Special counsel Robert Hur’s recent report on the president’s handling of classified documents — which found that criminal charges were not warranted, unlike in Trump’s own classified documents case — called Biden a “well-meaning elderly man with a poor memory.”

Both Trump and Biden have pushed back against concerns about their age and fitness. Biden has forcefully denied questions about his age, including in a contentious press conference defending his memory in the wake of Hur’s report. Trump responded to Haley’s attacks by touting his cognitive skills, saying he felt “about 35 years old.”

The survey also showed that voters largely support sending additional military aid to Ukraine, even as it has stalled in Congress. Among respondents, 56 percent were in favor and 44 percent were against more aid.

Voters were divided on providing further military aid to Israel in the war with Hamas, and overall slightly opposed it, 48 percent to 44 percent. The matter of sending aid to the U.S. ally has grown increasingly contentious as some lawmakers have raised humanitarian concerns about the effects of the Israeli offensive in Gaza.

The poll surveyed 1,421 registered voters nationwide and had a margin of error of plus or minus 2.5 percentage points.