Two polls of the 2024 presidential race released on Sunday showed former President Donald J. Trump cruising through the Republican primary — and a general election between two unpopular candidates if, as seems likely, the nominees are Mr. Trump and President Biden.

Each poll showed Mr. Biden with low approval ratings. One survey, from NBC News, showed the president’s disapproval rating at 56 percent, an all-time high for him in NBC polls. A second survey released on Sunday, by The Washington Post and ABC News, also showed 56 percent of voters surveyed as disapproving of his performance — though it included a general-election result that was far outside the range that other high-quality polls have found recently, which raised questions about the Post/ABC poll’s accuracy.

But when it came to personal favorability, Mr. Biden still fared better than Mr. Trump in the NBC poll: 39 percent said they had a very positive or somewhat positive opinion of him, compared with 35 percent who said the same of Mr. Trump.

In the Republican presidential primary race, the NBC poll had Mr. Trump leading his nearest rival, Gov. Ron DeSantis of Florida, by a gaping 43-point margin nationwide: 59 percent to 16 percent.

The race does not seem to have tightened as criminal indictments have piled up against Mr. Trump. In fact, his margin expanded from the 29 points that the last edition of the same poll found in June. But more than half the voters surveyed expressed concerns about his indictments.

The Washington Post/ABC News poll had some similar findings, with Mr. Trump leading Mr. DeSantis nationally by nearly 40 points.

The NBC poll found a hypothetical general election between Mr. Trump and Mr. Biden tied, with each candidate at 46 percent. It is the same picture that survey after survey has shown for months, underscoring how impervious partisan polarization remains to the influence of current events — and, for that matter, to opinions of individual candidates. At the same time, a series of special elections across the country has pointed to a more positive picture for Democrats, who have overperformed 2020 and 2016 presidential results by double digits.

But in the likely general election matchup, the Post/ABC News survey drew attention for how drastically it differed from what is otherwise a fairly steady consensus in recent polling.

The poll showed Mr. Trump leading Mr. Biden by 10 percentage points, a margin that no president has won by since Ronald Reagan in 1984. There were additional implausible results among subgroups of respondents: For example, the poll found Mr. Trump ahead by 20 points among voters younger than 35, a group Mr. Biden won by double digits three years ago.

The Post itself took the unusual step of describing its own result as an outlier.

Kevin Muñoz, a spokesman for Mr. Biden, dismissed it as well.

“President Biden is delivering results, his agenda is popular with the American people and we are mobilizing our winning coalition of voters well ahead of next year’s general election,” he said, adding, “We’ll win in 2024 by putting our heads down and doing the work, not by fretting about polls.”