"Senatorial courtesy" is a gesture of respect shown by the president to senators from the home state where a judicial vacancy occurs.
Senatorial courtesy permits senators of a proposed candidate's home state to object to the chosen one in light of the fact that the person may "personally obnoxious", or for comparative reasons. It is normal that the various senators support the contradicting congressperson's choice to veto the designation, to get a similar courtesy consequently. Senators practice this courtesy with the solid conviction that a similar support will be come back to them if the need ever emerges.