PORTLAND, Maine (AP) — Republican Sen. Susan Collins announced her reelection bid Tuesday, betting that she can hold onto her coveted Maine seat despite a renewed Democratic effort to oust her in a race that could determine control of the U.S. Senate.

The campaign will test Collins' political survival skills. The 73-year-old has won five terms by casting herself as a reflection of Maine's independent spirit, occasionally clashing with President Donald Trump while also largely supporting his agenda.

As she now seeks a sixth term, Collins faces outrage over immigration enforcement tactics that could become a political liability for Republican candidates across the country. A recent operation in Maine led to hundreds of arrests but also criticism that people were being rounded up even if they didn't have criminal records.

Collins has taken credit for stopping the surge of federal agents in Maine after she spoke directly with Department of Homeland Security Secretary Kristi Noem.

However, Democrats accused Collins of not going far enough, pointing to her refusal to call for Noem's ouster and her vote in favor of a bipartisan Homeland Security funding bill. The party needs to net four seats to retake the Senate majority, and they are aiming to do that in Maine, North Carolina, Alaska and Ohio.

Gov. Janet Mills and oyster farmer Graham Platner are among Collins' top Democratic challengers. While many establishment Democrats and influential left-leaning groups have backed Mills, Platner has gained traction with his anti-establishment image and economic equality message. He's campaigned aggressively while facing revelations of problematic social media posts and having to cover up a tattoo resembling a Nazi symbol.

Mills has accused Collins of governing “without any courage” shortly after the Republican voted in favor of funding the DHS and several other agencies in January. Platner has demanded that the agency be dismantled and said he did not believe Collins or the Trump administration's promise to leave Maine.

Platner recently outraised both Mills and Collins in campaign fundraising, according to the latest federal filings. The first-time candidate collected nearly $4.6 million, while Mills raised $2.7 million. Collins, who had not yet officially launched her campaign during the filing period, had more than $8 million in cash on hand at the end of 2025.

Collins, who has said she didn’t vote for Trump in 2016, voted to convict Trump after his 2021 impeachment over his role in the Jan. 6 Capitol riot. After Collins joined a handful of Republican colleagues in backing a failed effort to limit the president's ability to unilaterally use force in Venezuela, Trump said on social media that they “should never be elected to office again.”

But Collins has also broadly backed Trump's agenda, including his tax and spending bill, and his nominees.

Notably, Collins voted to confirm Robert F. Kennedy Jr. as Trump’s choice to be secretary of Health and Human Services. Kennedy has since espoused anti-vaccine policy and ousted public health officials at the Centers for Disease Control and Prevention.

She has faced down tough challenges before. Democrat Sara Gideon raised $69 million in 2020, outspending Collins in a bid to help take back the Senate during a presidential election year when the Democrats won the top of the ticket. Collins defeated Gideon by more than 8 points.

Collins has remained in office despite Maine becoming increasingly blue. The proportion of registered Democrats has increased since her last reelection campaign, when “unenrolled” independent voters outnumbered Democrats in 2019 but now trail them in 2026. Republicans have trailed both groups for years.

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Kruesi reported from Providence, Rhode Island.