The campaign of Rhode Island Lieutenant Governor Sabina Matos, who is a candidate in the Democratic Party Primary for US House, 1st District, Rhode Island, on Tue, Sept 5:
https://en.wikipedia.org/wiki/2023_Rhode_Island%27s_1st_congressional_district_special_election
has been accused of gathering fraudulent signatures. Here is a story on this matter. Ms. Matos has blamed an outside signature “vendor” for submitting bad signatures and has said that she will not withdraw from the race.
I am not sure why a major party candidate would need a signature vendor, as the signature requirement for US House elections in Rhode Island is 500 signatures within a district.