LANSING, Mich. (AP) — Fraudulent signatures could upend Michigan’s congressional races this year as each declared GOP U.S. Senate candidate faces new calls to investigate their attempts to get on the August primary ballot and a Democratic U.S. House candidate appears likely to fall short.

Just two years ago, multiple high-profile gubernatorial campaigns fell into the same trap and lost access to the ballot.

Adam Hollier, a former state senator who has garnered significant Democratic support in his primary challenge of U.S. Rep. Shri Thanedar, is expected to be kept off the August primary ballot after county election staff found he did not have enough valid signatures on nominating petitions.

Republicans vying for Michigan’s open U.S. Senate seat are now facing similar allegations after state and national Democratic groups submitted a request that their nominating petitions be investigated on Friday.