Collins told colleagues at a small Senate prayer breakfast meeting last week that she still felt lingering resentment toward Democratic senators who campaigned against her in Maine.

She confessed that she had “trouble forgiving colleagues” who traveled to Maine and told voters she was “a Bush clone and called into question her ethics,” said a senator who attended the meeting.

Collins’s lingering resentment could emerge as a snag for Democratic leaders who expect her to side with them on many important votes.