U.S. Sen. Susan Collins, R-Maine, talks Friday morning with Ben Tucker, regional representative for U.S. Sen. Angus King Jr., I-Maine, as she arrives for the groundbreaking ceremony at the PAL Center in Auburn. Russ Dillingham/Sun Journal

AUBURN — U.S. Sen. Susan Collins, a Maine Republican, said Friday that she watched the first presidential debate with “a sense of sadness” as she observed President Joe Biden struggle.

“I think all of us have had the experience with a loved one or a co-worker or a close friend and have seen cognitive decline,” said Collins, who has known Biden for almost three decades.

Biden has repeatedly insisted his mental state is fine and that he simply had “a bad night” when he faced Trump on national television last month. His doctors six months ago expressed no concern after examining him.

While there has been no medical evidence released indicating the president’s mental acuity is declining, that hasn’t stopped even some Democrats, including some longtime allies of the president, from raising questions about whether he is slipping.

Collins said it was up to Biden, his family and the Democrats “to decide who their nominee is” and declined to offer her advice.

Collins, who has said she did not vote for Republican Donald Trump in either the 2016 or the 2020 presidential elections, is among a dwindling group of GOP senators who have sought to stay true to her party’s traditional values without embracing Trump.

Biden’s poor showing at his first debate against Trump, whose energetic bluster stood in stark contrast to a fumbling Biden, has spurred considerable talk among Democrats of potentially finding a new presidential nominee for this year’s general election.

Collins was in the city Friday for the groundbreaking for a new PAL Center in Auburn.