Former Vice President Joseph R. Biden may be firmly in control of the 2020 Democratic presidential race, with a double-digit lead — or he could be stuck in a three-way tie.
The state of play in the race is more convoluted than ever, with polls showing vastly different playing fields as the candidates head into Labor Day.
One respected polling outfit, Monmouth University, showed Mr. Biden trailing Sens. Bernard Sanders and Elizabeth Warren, both tied at 20% support, with Mr. Biden 1 point behind. That marked a 13-point drop for Mr. Biden since June.
But another pollster, Morning Consult, released a survey Tuesday showing Mr. Biden still easily ahead of his challengers, with a third of potential Democratic primary voters and caucus-goers picking him. Mr. Sanders trailed in that poll at 20%, with Ms. Warren a further 5 points behind.
“The likelihood — one of them is wrong. And you might argue, well, both of them could be wrong to some extent,” said Ron Faucheux, president of Clarus Research Group, a research and polling company. “The best way to read polls is to wait for the next two or three and see where they are. If something comes out that looks like an outlier, just wait and see.”
For now, the Monmouth survey is looking like the outlier.
An Emerson College poll released Tuesday had Mr. Biden at 31% support, followed by Mr. Sanders at 24%, Ms. Warren at 15%, and Sen. Kamala D. Harris at 10%. And the Real Clear Politics average of recent polling showed Mr. Biden holding about a 10-point lead nationally, with Mr. Sanders and Ms. Warren duking it out for second place.
“I’m a big one for going after the average,” said G. Terry Madonna, director of the Franklin & Marshall College poll. “It’s really not easy to get into one poll and say, well, you’re right or you’re wrong.”
Analysts say there is reason to believe Mr. Biden could be losing support, with his campaign trail gaffes drawing the wrong kind of attention. He recently confused New Hampshire with neighboring Vermont and told attendees at the Iowa State Fair that “we choose truth over facts,” among other verbal misfires.
“The last few weeks haven’t looked good for him,” Mr. Faucheux said. “To see his numbers go down some would not be a big surprise.”
Monmouth, which showed a 13-point drop for Mr. Biden from June, found him sliding particularly among Democrats who considered themselves “moderate” or “conservative.”
He had held a 30-point lead over Mr. Sanders among that group in June but just a 2-point edge over him in the most recent poll.
“Moderate voters, who have been paying less attention, seem to be expressing doubts about Biden,” said Patrick Murray, director of the Monmouth University Polling Institute.
Mr. Biden’s standing among moderates, though, has been better in other polling that has shown him comfortably in front.
Though Monmouth is generally praised as one of the more reputable national polling outfits, the results of this week’s poll were based on a relatively small sample size, which can create higher margins of error and bigger swings in individual polls.
The sample sizes of respondents in the surveys ranged from 298 in the Monmouth poll to 627 in the Emerson poll and more than 17,000 in the Morning Consult poll.
Mr. Madonna said a sample size of between about 600 and 800 respondents would be preferable for a national poll, but that it nevertheless appears the race is getting more competitive.
“Do I think the race is tighter? The answer is yes,” he said.
But Michael G. Miller, a political science professor at Barnard College in New York, wasn’t sure about how much slippage there’s been.
“It’s the summer. People aren’t paying attention but they know the name Joe Biden. They associate positive feelings with him — they’re simply just not shopping around yet,” said Mr. Miller, who also cautioned against drawing broad conclusions from national primary polls.
“And so as they actually do that work, we should expect people to move a little bit,” he said. “I’m not sure that that indicates anything about failure of Biden’s campaign or anything else — it’s just a natural statistical principle.”