Former Rep. Michael "Ozzie" Myers pleaded guilty to frequently stuffing ballots, conspiring to illegally vote in a federal election and deprive civil rights, voting records falsification, and bribery in favor of Democratic candidates, according to a Department of Justice press release. He carried out the schemes in Pennsylvania during the 2014, 2015, 2016, 2017 and 2018 elections, the DOJ said.
I'm sure he is the only one.

Former Dem Rep gets 30-month prison sentence in ballot-stuffing election fraud case
Former Pennsylvania Rep. Michael "Ozzie" Myers pleaded guilty in an election fraud case in which he bribed election officials to stuff ballots for Democratic candidates.