Explainer: Why Election Day could be just the start of a long battle over the U.S. presidency

FILE PHOTO: A resident drops off a mail-in ballot at the Edmondson Westside High School Polling site in Baltimore, Maryland, U.S., April 28, 2020. REUTERS/Tom Brenner/File Photo

(Reuters) - President Donald Trump's refusal this week to say if he would accept the results of November's election, and his repeated assertions that the vote will be "rigged" because of mail-in ballots, have raised the spectre of a disputed election that could take weeks, or even months, to resolve.

Even absent allegations of fraud, the deluge of mail ballots due to the coronavirus pandemic could take weeks to tally, making it less likely a winner is declared on Election Day in the contest between Trump and Democrat Joe Biden. The former vice president currently leads Trump in opinion polls.