Majorities of Americans in a new survey have doubts about the mental capabilities of both President Biden and former President Trump, as their age develops as a central focus in a likely general election rematch.

Roughly 6-in-10 respondents said they’re not very or not at all confident in Biden’s mental capability to serve another term as president, according to the survey from The Associated Press and NORC Center for Public Affairs Research. About the same proportion also held doubts about Trump’s mental capacity.

Biden, 81, is the oldest sitting U.S. president. Trump. 77, would be the oldest president in the country’s history at the end of a second term. A series of gaffes by both candidates in recent months, repeatedly mixing people up and misspeaking, has also sparked concerns.

The new findings come as the race for the White House approaches the general election, with Super Tuesday expected to seal Trump’s GOP nomination and Biden not facing any major competition. 

About a third of Democrats in the new survey say they’re not very or not at all confident in Biden’s mental capability, up from 14 percent in January. Just 40 percent of Democrats said they’re extremely or very confident in Biden’s mental abilities.

Independents, meanwhile, are much more likely to say that they lack confidence in Biden’s mental capabilities compared with Trump’s, 80 to 56 percent.

Pollsters also found that Biden has a 36 percent overall approval rating ahead of his State of the Union speech on Thursday evening, with low ratings specifically on immigration (29 percent approval), the Israel-Hamas war (31 percent) and the economy (34 percent).

And even though about 57 percent of survey respondents said the economy is worse off now than when Biden took office, just over half also said their personal finances are in good standing, about 54 percent.

The AP-NORC poll surveyed about 1,100 people over the course of last week, with a margin of error of 4.1 percent.

The Associated Press contributed.