Most Arab Mushriks (polytheists) believed in Allah as their God and creator but they will associate partners with Him.
“And most of them believe in Allah, but commit shirk. “(Surah Yusuf, verse 106)
“If indeed thou ask them who has created the heavens and the earth and subjected the sun and the moon, they will certainly reply, “Allah”. And if indeed thou ask them who it is that sends down rain from the sky, and gives life therewith to the earth after its death, they will certainly reply, “Allah!” (Surah Ankabut, verses 61-63)
“Is it not to Allah that sincere devotion is due? But those who take for protectors other than Allah (say): “We only serve them in order that they may bring us nearer to Allah.” (Surah Zumar, verse 3)