Maine Gov. Janet Mills suspends her US Senate campaign

Maine Gov. Janet Mills announced Thursday morning that she is suspending her U.S. Senate campaign, leaving Graham Platner as the likely Democratic nominee to face off against incumbent Republican Sen. Susan Collins.

Mills cited financial resources as a reason for suspending her campaign.

“While I have the drive and passion, commitment and experience, and above all else -- the fight -- to continue on, I very simply do not have the one thing that political campaigns unfortunately require today: the financial resources,” Mills said in a prepared statement. “That is why today I have made the incredibly difficult decision to suspend my campaign for the United States Senate."

The latest Federal Election Commission filings from Q1 show Planter raised roughly $1.4 million more than Mills and has roughly $1.7 million more cash on hand.

Platner, an oyster farmer and military veteran, also regularly polled significantly higher than Mills.

Mills' announcement came just one day before the Maine Democratic Convention was scheduled to begin -- and more than five weeks before the state's June 9 primary.

Mills and Platner were scheduled to participate in their first televised debates of the campaign in May alongside David Costello.

Sen. Bernie Sanders supported Platner, while Sen. Chuck Schumer had previously announced his endorsement of Mills.

In a statement issued Thursday morning by the Democratic Senatorial Campaign Committee, Schumer and Sen. Kirsten Gillibrand said in part, “After years of allowing Trump’s abuses of power, Senator Collins has never been more vulnerable and we will work with the presumptive Democratic nominee Graham Platner to defeat her.”

ABC News' Hannah Demissie contributed to this report.