It is not the law that a senator suggests a nominee for a circuit court. It is a long standing tradition. I believe it is allowed to stand because the senate must vote on each nominee. And the nominating Senator often acts as shepherd for the nominee to get through conference hearings.
As someone posted earlier, this situation may be a compromise that assumes the republicans will/might lose control of the senate in January.
Thank you for that perspective. Funny...it never occurred to me what the full process was until today.