As they state towards the bottom of the page this specific poll was conducted online:

On June 28, 2024, Data for Progress conducted a survey of 1,011 U.S. likely voters nationally using web panel respondents. The sample was weighted to be representative of likely voters by age, gender, education, race, geography, and 2020 recalled vote. The survey was conducted in English. The margin of error associated with the sample size is ±3 percentage points. Results for subgroups of the sample are subject to increased margins of error. Partisanship reflected in tabulations is based on self identified party affiliation, not partisan registration. For more information please visit dataforprogress.org/our-methodology

While it’s true that polls can vary widely and are sometimes unreliable, it’s worth noting that according to their 2020 retrospective conservative white voters tend to be underrepresented, while liberal voters and activists are overrepresented in their surveys. This is consistent with a previous analysis by FiveThirtyEight showing that in 2019-2020 polls substantially overestimated Democratic performance.