According to this story, the Maine Republican Party is launching a referendum petition against the law that passed last year to use ranked choice voting for president in the 2020 general election, and in future presidential primaries and elections. If the party gets enough signatures, the measure would not be in effect in November 2020. Instead, the voters would vote on whether to retain ranked choice voting for president.
The petition drive would have no effect on using ranked choice voting for congressional elections.