I think they meant that AOC could threaten him in the congressional district Schumer lives in and win. She could easily then challenge him, in the future, for his senate seat, but seems she is rather a potential candidate for a POTUS campaign, in 24.
Lets watch Schumer defend her, or not. There may be a story there, either way. Shes definitely a rolling political pressure cooker, for Democrats, especially those in NY.