Republican Senator Susan Collins has sparked health concerns after appearing to shake in a re-election campaign advert.

The 73-year-old Maine Senator is seen unboxing a pair of sneakers in the video, her hands trembling as she opens the package, head twitching and voice quavering.

'This is perfect for 2026 because I'm... running,' Collins says shakily as she holds up one of the sneakers.

The video sparked concerns for her health with journalist Ken Klippenstein posting on X that she appeared to be 'vibrating like an electric toothbrush.'

Others questioned whether she was healthy enough to seek re-election.

Collins, who assumed office in 1997, is running for a sixth term and faces Democrat Graham Platner in November's Senate race.

Others said that while they do not support the GOP Senator, who has been an outspoken critic of Donald Trump, her shaking should not count against her.

'I don't agree with her but just because she shakes doesn't really mean anything,' said one X user.

Collins' shaking is not new and has been discussed following previous appearances dating back to at least 2019.

The re-election campaign advert was first posted in February but went viral today and sparked a wave of concern, as well as criticism amid calls for term limits.

'Any other job in America will fire you if you can't perform due to health reasons but somehow politicians just get to keep milking it and doing nothing,' wrote one commenter.

US Senators have six-year terms but there are no federal term limits, meaning they can keeping seeking re-election indefinitely.

Trump turned on Collins after her Venezuela war powers vote in January, urging voters to oust her and saying she 'should never be elected to office again.'

Republicans are defending 22 Senate seats in November as they fight to protect Trump's 53-47 majority. 

Collins has been contacted for comment.