This percentage result came from asking a “forced choice question”, as in “If you had to choose, would you say you lean towards supporting Donald Trump or Joe Biden?” to which the poll explains as “Forced choice only asked of those who said ‘some other candidate’, ‘I would not vote’, or ‘not sure’ in initial question, and combining definite with leaning.
Unforced, the sample still gave Biden a double-digit lead over Trump, and just shy of an outright majority at 49% to 38% among registered voters – with 6% for other candidates, 5% undecided, and 1% not going to vote. Read more at Ipsos.