PORTLAND (AP) — Maine’s GOP gubernatorial primary could become more heated after Republican U.S. Sen. Susan Collins announced she won’t run.

The gubernatorial race is already a crowded field, with more than a dozen candidates announcing primary runs. Three Republicans and nine Democrats have registered to run, while five unaffiliated and third-party candidates have also registered. But there may be more to come.

Collins was seen as a favorite to keep Republicans in the governor’s mansion, so some Republican candidates were waiting on her decision on Friday before announcing whether or not to run, according to several GOP experts, such as former Republican state Sen. Phil Harriman.

Maine Republicans have touted their recent success at electing and re-electing candidates to Congress, the governorship and the state Legislature, where the GOP maintains control of the Senate. Republican President Donald Trump won one of Maine’s four electoral votes thanks to support from its 2nd Congressional District, which includes the portion of the state north of Portland and Augusta.

So far, the Republican gubernatorial primary will include former Maine Health and Human Services Commissioner Mary Mayhew, of South China; Senate Majority Leader Garrett Mason, of Lisbon; and House Minority Leader Ken Fredette, of Newport.

“Thanks to the work of Democrats, Republicans have had to spend the last seven years fixing Maine’s economy,” Fredette said.

Fredette told the Portland Press Herald that if Collins had decided to run, she might have been a dominant force in the race. He said other candidates that have waited to announce their runs may lack a clear vision for where they want to take Maine.

The race could also include the owner of auto-body repair chain Moody’s Collision Centers, Shawn Moody. He announced this week that he registered as a Republican and plans to seek the party’s nomination. Lobbyist and former Republican House leader Josh Tardy has also said he’s considering a gubernatorial run, but didn’t immediately respond to a request for comment Saturday.

Maine Democratic Party Chair Phil Bartlett said Republican gubernatorial candidates represent the party’s fringe who support four more years of GOP Gov. Paul LePage. The governor is term-limited from running in 2018.

“The election next November will be a clear choice between four more years of these backward LePage-Trump policies, or a Democrat who will bring real change to Augusta by focusing on creating jobs, growing our economy, and building a stronger, more prosperous Maine,” Bartlett said.

Sen. Susan Collins, R-Maine, smiles during a news conference Friday, Oct. 13, 2017, in Rockland, Maine, after announcing she will remain in the U.S. Senate and not run for governor. (AP Photo/David Sharp)