This morning Janet Mills announced she was suspending her campaign, seemingly setting the stage for what could end up as one of the most competitive Senate elections this cycle. Graham Platner will likely be the Democratic nominee to take on incumbent Senator Susan Collins (R). The primary has seen $53M in total ad spending, making it the most expensive Senate primary on record in Maine. With two months left to go, the contest has already surpassed the 2020 Senate primary total of $36M. Nationally, Maine currently ranks as the fourth most expensive Senate primary of the 2026 cycle, trailing Texas, Illinois, and Kentucky.
So far in the primary, Republican advertisers have spent $33.0M compared to $20.1M from Democrats. Collins is seeking a sixth term and has a history of winning competitive and expensive elections. In 2020, she overcame $67.9M in Democratic ad spending in her successful re-election campaign. So far this cycle, her campaign has aired $768K in ad spending, significantly behind her 2020 pace, when she spent $4.4M. However, Collins has seen $19M more in aired ad support than at this point in 2020. In total, she’s seen $26.9M in aired ad support from outside groups, led by One Nation ($17.7M), Stronger America ($7.0M), and American Advancement ($846K), among other groups.
On the Democratic side, Platner remains the lone active candidate with linear ad spending backing him. Platner’s campaign has spent $7.1M, with $112K in future reservations. Prior to dropping out, the Mills campaign spent $1.8M, with her last linear ad airing on April 10th. Planter, however, has remained on air continuously since January 27th. No outside group has placed any linear ad spending supporting either candidate, but Democratic groups have aired $9.1M attacking Collins. Their ads target Collins on ICE, inflation, and the conflict in Iran.
Platner’s ads have focused on affordability and healthcare. He’s lobbed attacks at both President Trump and Collins, highlighting her support for “Trump’s war on Iran”. While Platner avoided attacking Mills, the governor launched two attack ads targeting Platner. These ads feature women reading comments Platner made online about sexual assault, among other controversial topics. Platner responded with an ad denouncing his past comments and asking Maine voters to evaluate him based on who he is today rather than past remarks.
Republicans have wasted no time attacking Platner. On April 27th, pro-Collins group Pine Tree Results PAC launched an attack ad on Platner, highlighting his past online comments and his controversial tattoo.
Both parties are already investing heavily in the state, which leads the cycle in reserved general election ad spending at $67.8M. Republican-aligned Senate Leadership Fund has pre-booked $28.7M in advertising for the general election. This total already exceeds the group’s entire spending in Maine during the 2020 cycle. Additionally, Pine Tree Results PAC ($18.1M) and Stronger America ($607K) have reserved airtime to support Collins during the general election.
On the Democratic side, WinSenate has reserved $20.4M in advertising for the general election. Unlike Senate Leadership Fund, WinSenate has only placed reservations in Maine at this point.
The scale and timing of these reservations signal that both parties are preparing for a highly competitive general election, with advertisers reserving ad space months before the primary ends.