Republicans are preparing an $8 million advertising campaign aimed at the Democrat candidate who could replace Graham Platner in the Maine Senate race, hoping to define the challenger before Democrats can introduce a new nominee to voters.

Axios reported that Pine Tree Results, a Republican-aligned super PAC supporting Sen. Susan Collins, is planning the ad campaign as Democrats face uncertainty over whether Platner will remain in the race.

The planned spending comes as Platner faces pressure to withdraw after allegations of sexual misconduct, which he has denied, putting Democrats in the position of potentially selecting a replacement candidate ahead of the November election.

Under Maine election law, Democrats have a limited window to replace their nominee if Platner exits the race, with several potential candidates already being discussed.

Republicans are seeking to take advantage of the uncertainty by launching their campaign before Democrats' replacement candidate has time to build name recognition or define his or her own message.

Pine Tree Results has raised $10.5 million so far this year, according to Axios, giving the group significant resources for a major media effort in one of the country's most closely watched Senate contests.

The Maine race is considered a key Senate battleground as Republicans defend Collins' seat and Democrats look for opportunities to gain ground in the chamber.

Potential Democrat replacements include former Maine CDC Director Nirav Shah, Maine Secretary of State Shenna Bellows, and former state Senate President Troy Jackson, though Democrats have not selected a new nominee.

Republicans are betting that an early advertising advantage can shape voter perceptions of the Democrat nominee before the race enters its final stages.