On the day Donald Trump endorsed him as a tireless advocate for New Jersey’s seventh district, the representative Tom Kean Jr was, as he has been since early March, nowhere to be found.

Kean, a New Jersey Republican, was last seen when he cast a House floor vote on 5 March, and he is running unopposed in Tuesday’s Republican primary. The Democratic race in his district, meanwhile, has attracted multiple candidates and ample fundraising.

In late April, his office said he was dealing with a “personal medical issue” and would be back “very soon”. He told the New Jersey Globe last month he expected to return within “the next couple of weeks”. In the meantime, Kean’s social media accounts have continued posting regularly, with staff attending ribbon-cuttings and graduation ceremonies on his behalf.

“Tom is working tirelessly to Keep our Border SECURE, Stop Migrant Crime, Grow our Economy, Cut Taxes and Regulations, Champion Small Business, Unleash American Energy DOMINANCE, Support our Brave Military and Veterans, and Protect our always under siege Second Amendment,” Trump wrote on Truth Social late on Monday night.

The House speaker, Mike Johnson, who has reportedly spoken with Kean privately, has not been given a return date, three Republican leadership sources told CNN.

Kean’s Republican colleagues, according to CNN, say they are worried about his health – and about holding a seat that four Democratic candidates, each having raised over $1m, are lining up to contest in November. Some have begun asking what New Jersey law would require if Kean were unable to continue after winning tonight’s uncontested primary.

Multiple staffers in his office did not respond to a request for comment on whether Kean was aware that he had been endorsed by Trump, and if he is doing well.