"38% of Likely US Voters think Biden is suffering from some form of dementia," the conservative-leaning pollster said in a statement summarizing the poll.
The poll also showed that 20 percent of voters within Biden's own party believe he has this type of mental disorder compared to 66% of Republicans and 30% of independents.
The Biden campaign has slammed the Republicans for trying to "smear" the presumptive Democratic nominee by questioning his mental health just as President Donald Trump continues to fail the American people.