DES MOINES — A regular visitor to Iowa during the months preceding the February presidential caucuses, Joe Biden made Democrats here wait until almost the final moment of the 2020 campaign to see him again.Time soon will tell whether the trip was worth Biden’s effort. But on Friday, four days before Election Day, the former vice president thrilled hundreds of supporters with a drive-in-style campaign rally at the Iowa State Fairgrounds in Des Moines.Biden, the Democratic presidential nominee, is locked in a close race in Iowa with Republican President Donald Trump, according to numerous polls.