Then he cancels out any political advantage this might have given him by being the one politician to donate to Bob Menendez's legal fund. Even Hillary didn't want Menendez's endorsement.
The donations were several years ago. But republicans are going to use this against him if he runs. They have also been callling for the senators who received campaign cash from Menendez to return the donations. (It includes possible 2020 contenders like Kaine, Murphy and Warren who took between $ 5000-10000 from his PAC.)