“There is an old Senate tradition going back to when George Washington was president called ‘senatorial courtesy,’ in which home state senators get a virtual veto over executive appointees with jobs that exist entirely within their home state,” Ian Ostrander, a political science professor at Michigan State University, told us via email. “Senatorial courtesy is the tradition that led to the more familiar blue slips process for court appointments in the Senate Judiciary Committee.”
Under the so-called blue-slip policy, in order to be presented to the Senate for a vote, a judge or U.S. attorney nominated by the president must get the signoff, or blue-slip approval, from home-state senators.
“Given the tradition, Trump is right that the two home state senators had a say in the approval of the US Attorney for Delaware in that the senators’ refusal to accept the nominee would have ended the nomination,” Ostrander said. “Knowing this, presidents (or more accurately their staff) will consult the relevant home state senators before making a nomination. Sometimes this leads to a suggestion from the senators that is accepted and nominated by a president.”
That’s apparently what happened with Oberly’s replacement, David Weiss, who once served as the acting and interim United States attorney for the District of Delaware.
According to the Associated Press, Carper and Coons in November 2017 “recommended Weiss to the White House for the job.”