Senate Republicans are treating Graham Platner’s exit from the Maine Senate race with a sense of urgency and want to avoid being caught flat-footed as Democrats prepare to field a new candidate.

National and state Republicans have begun pulling together all of the opposition research done earlier in the cycle, according to a source familiar with the planning, as a large field of Democrats, most of whom ran for House, Senate, or governor this year in Maine, enter the race to replace Platner.