Oct. 11 (UPI) — Maine Gov. Janet Mills is expected to launch a campaign on Tuesday to unseat longtime U.S. Susan Collins, R-ME, according to internal campaign documents and a now-deleted social media post.

According to a campaign document first reported by Axios and since confirmed by several other news organizations, Mills plans to join the Democrat primary field for Collins’ seat next year, as she is term-limited and cannot run for re-election as governor.

Democrats have been recruiting Mills to run against the five-term Sen. Collins, who is thought by party leaders to be vulnerable based on her low approval ratings, the Portland Press Herald reported.

A video launching the campaign was also briefly posted to Mills’ X account, which directed viewers to an ActBlue web page for donations, Fox News reported on Friday evening.

According to Fox, Mills said she is “running to flip Maine’s seat blue” because Collins has “sold out Maine and bowed down to special interests and to Donald Trump, but that ends now.”

Mills has gained national attention after breaking publicly with President Donald Trump at a White House event when he pushed to exclude transgender women and girls from female sports.

Although the five-term incumbent Collins is regarded as a moderate and has broken with Trump, as well as her party, in the past, the Democratic Senatorial Committee has made the Maine seat a priority, CBS News reported, and Fox noted that Mills is favored for the seat by Sen. Minority Leader Chuck Schumer, D-NY.

Collins in 2020 beat Democrat nominee Sara Gideon by nearly 9 points even though Gideon spent nearly twice on her campaign as Collins, $62.9 million compared with $29.6 million.

Before Mills can face off with Collins, however, she will have to wade through the Democratic primary, which already features the Sen. Bernie Sanders-endorsed progressive oyster farmer Graham Platner, former End Citizens United vice president Jordan Wood and brewery owner Dan Kleban.