Jesus Christ, you are NOT an English speaker, are you?
"Long odds" or "the longshot" means that the bookies do NOT think that person will win and so consider it safe to take heavier bets from you.
The bookies are, as far as I can see, nervous to take bets for Biden and confident to take bets for Trump - because they all think Biden will win. They don't want to pay out for Biden bets but they'll take your money for Trump bets because they don't think he'll win.
You, being confident of the opposite, should place bets with them on Trump and win big. Because you're so smart. You don't know what any of this means but obviously you know better about the election, right? So get that money on it - as much as you can borrow.