Mr. Biden, the Democratic Party and their shared accounts now have $155 million cash on hand — up from $130 million at the end of January. The Trump campaign has not released its February fund-raising figures but has said it also had its strongest month among small donors — topping the $22.3 million raised last August. Mr. Trump has been schmoozing with donors at Mar-a-Lago, his private club and residence in Palm Beach, Fla.