Who is "Elokim" that he should ask?
Radak. Like Targum Yonasan: They thought that he will ask Hashem.
Radak citing Shevu'os 35b: It is idolatry, for every Elokim in the Parshah is Chulin, except for (18:31) "Kol Yemei Heyos Beis Elokim b'Shilo." 1
Radak: How can one say that "Ki Nesanah Elokim b'Yedchem" is Chol?! R. Eliezer (35b) says that in this Parshah, only "... Elokim b'Shilo" and the names Aleph-Dalet are Kadosh. This is unlike Targum Yonasan on our verse.
How will he ask Elokim?
Rashi: Via Terafim, which speak through witchcraft. 1 Malbim - they thought that the Terafim can tell the future.
Radak: If Elokim is Chol (refer to 16:5:1:2), he enticed them to believe that the Terafim can tell the future. Refer to Bereishis 31:19:1:1,4.
