Fox Corp. shares tumbled with speculation ramping up that President Donald Trump might back or launch a rival news service after he leaves office.

Axios reported Thursday, citing unidentified sources, that Trump is planning a subscription-based streaming platform similar to Fox Nation, a $6-a-month service launched two years ago.

Fox shares declined from the start of trading, and the drop deepened after Trump amplified a series of Twitter posts from users criticizing Fox News as insufficiently loyal to the president and urging conservatives to switch to rivals such as Newsmax.