The corruption retrial of former jails guard union head Norman Seabrook kicks off Wednesday, but once again it is Mayor de Blasio who is expected to be on the hot seat — over his dealings with confessed briber and star government witness Jona Rechnitz.

At Seabrook’s first trial in 2017, which resulted in a hung jury, Rechnitz testified for days about his efforts to buy influence with a wide swath of public officials, including Seabrook.

Rechnitz also said he raised and donated hundreds of thousands of dollars for de Blasio on the expectation that it would buy him special access to City Hall.