The Harris campaign warned on Friday that Republican presidential candidate Donald Trump is likely to declare victory before all votes are calculated, the campaign's aide told reporters.
"He did this before - it failed. If he does it again, it will fail," RealClearPolitics (RCP) correspondent Philip Wegmann quoted the person as saying.
The latest CBS News poll released earlier this week showed a tied race in Pennsylvania, with both Donald Trump and Democratic candidate Kamala Harris each holding 49% of the vote.