Graham Platner, the presumptive Democratic nominee for U.S. Senate in Maine, is working to unite his party ahead of the general election against Republican incumbent Susan Collins while facing criticism over past social media comments about sexual assault.

At the Maine Democratic Party convention, attendees expressed relief at focusing on the general election campaign. However, some party members indicated mixed feelings about their prospects in the race against Collins, who has held the seat since 1997.

The campaign has been overshadowed by controversy surrounding social media posts Platner made in 2013, which were uncovered by The Washington Post last year. In those posts, Platner downplayed the difficulties service members face regarding sexual assault issues, according to the reporting.

Rep. Debbie Dingell (D-Mich.) publicly criticized Platner's past comments, stating she was "very upset" by the social media posts from more than a decade ago. Her remarks highlight concerns among some Democrats about the candidate's past statements on the sensitive topic.

The controversy comes as Platner seeks to consolidate Democratic support for what is expected to be a competitive Senate race in Maine. Collins has been considered a moderate Republican throughout her tenure but faces a Democratic challenge in a state that has shown competitive races in recent election cycles.

Platner will need to address the lingering concerns about his past comments while building a coalition capable of challenging Collins' long-standing position in Maine politics.