According to the latest NBC News national poll, three-quarters of voters, including half of Democrats, say they have concerns about U.S. President Joe Biden's mental and physical health.

Meanwhile, 61% of voters are concerned about former President Donald Trump's multiple felony convictions, with less than half of voters concerned about his mental and physical health.

The results are essentially unchanged from September, when the NBC News poll first asked about these concerns - and at that time, more voters said they were concerned about Biden's age (he's now 81) than about Trump's legal troubles. Trump is 77 years old.

When asked if Trump has the mental and physical health necessary to be president for a second term, 48% said they had concerns.

According to the new poll, 76% of voters said they have serious (62%) or moderate (14%) concerns that Biden does not have the necessary mental and physical health to be president for a second term, compared with 24% who have minor concerns (13%) or no concerns at all (11%).

Along party lines, 95% of Republican voters, 81% of independents and 54% of Democrats say they have serious or moderate concerns about Biden's suitability for a second term.

By comparison, 61% of all voters said they have serious (51%) or moderate (10%) concerns about Trump facing multiple criminal and civil trials for wrongdoing, including criminal charges for trying to undo the results of the 2020 election. Thirty-nine percent said they have little (11%) or no concern (28%).