A Senate aide for Sen. Susan Collins already facing an ethics complaint over doing political work was quoted on Twitter on Tuesday discussing the senator’s political campaign.

Collins, R-Maine, was slated to attend a fundraiser for her re-election campaign on Thursday in Houston alongside Sen. John Cornyn, R-Texas, but canceled the trip to vote on proposals to end the government shutdown.

After the fundraiser was noted in a tweet by Dave Levinthal, a journalist with the Center for Public Integrity, Collins’ Senate office communications director, Annie Clark, reached out to Levinthal to tell him the event was off.

“(Clark) tells me the Thursday fundraising event in Houston has been canceled. (Clark noted Collins’ excellent record of being present for Senate votes,” Levinthal tweeted.

Earlier this month, the American Democracy Legal Fund asked the Senate Select Committee on Ethics to investigate Clark after she wrote an op-ed in the Bangor Daily News criticizing Maine’s House speaker, Sara Gideon, a Democrat and a potential challenger to Collins next year.

“One would think she would be working feverishly to prepare for the upcoming legislative session. But as we saw from her Dec. 18 BDN column, she is far more concerned with her personal political ambitions for 2020,” Clark wrote, referencing the possibility that Gideon will run to unseat her boss.

Clark also criticized Gideon’s position on the Affordable Care Act in political terms.

“If Gideon looked beyond her far left-wing talking points, she might see the basic unfairness behind penalizing people who can’t afford to buy insurance for not buying insurance,” she wrote. “The Democrats in the U.S. Senate seemed to understand this – because not a single one of them offered an amendment to save this ill-advised mandate.”

The piece identified her in her as the “communications director for U.S. Sen. Susan Collins.”

ADLF called it a violation of Senate ethics rules.

“By using her official Senate staff title to pen an op-ed attacking a local official who she herself casts as a potential opponent of Senator Collins in 2020, Ms. Clark has violated the Senate’s longstanding rule against using official resources for campaign activity,” Brad Woodhouse, ADLF’s director, wrote in a letter to the Ethics Committee.

Collins is a seeking a fifth term in the Senate but is expected to face a difficult path to re-election in a state where Donald Trump received only 45 percent of the vote in 2016 and a Democrat won the governor’s race in November.