President Donald Trump on Monday concurred that Sen. Susan Collins’ (R-ME) re-election bid is critical for Senate Republicans to maintain their majority in the upper chamber.

President Trump wrote on Twitter that he “100%” agrees with Sen. Lindsey Graham (R-SC), who tweeted Friday that Collins demonstrated “unbelievable courage” by voting in favor of then-Supreme Court Justice nominee Brett Kavanaugh and that the Maine Republican is needed to keep control of the Senate.

Collins officially kicked off her re-election campaign in an email to supporters in which she touted her “bipartisan commonsense approach” will be important in an era of bitter partisanship.

“I wanted to think hard about whether there’s still a role in Washington for someone who’s in the middle who believes in bipartisanship, compromise and collegiality. Those used to be the hallmarks of the Senate but in recent years have become increasingly rare as the Senate has become more and more polarized,” she told the Associated Press.

Collins refused to vote for Trump in 2016. She chose to write in House Speaker Paul Ryan after she criticized Trump for attacking members of marginalized groups, the Sun Journal reported.

Potential Democratic challengers to Collins include Maine House Speaker Sara Gideon and Betsy Sweet, former director of the Maine Women’s Lobby. The state primary is in June.

The Associated Press contributed to this report.