How many gods did the Jews worship?

Answer 1

From the time of Abraham, one God. Abraham worshiped "the Lord God of Heaven and Earth" (Genesis 14:22 and 24:3) and complained about the Philistines' lack of fear of God (Genesis 20:11).
Jacob confiscated the idolatrous images taken from Shechem (Genesis 35:2) and got rid of them (Genesis 35:4); and refrained from invoking the gods of Nahor (Genesis 31:53). Rachel pilfered Laban's statue-images (Genesis 31:19) in order to prevent him from idolatry (Rashi commentary, ibid.). Joseph placed his hope in the God of the Forefathers (Genesis 50:24).
At the time of the Exodus, God wrecked the Egyptian idols (Exodus 12:12) and warned against idolatry (Exodus 22:19). Later, Moses characterized the Golden Calf as "a great sin" (Exodus 32:21, 30) and punished the worshipers (Exodus ch.32). During the rest of his lifetime and that of Joshua (Judges 2:7), no incidents of Israelite idolatry were reported.
There were times when some (or many) of the Israelites went astray after foreign gods (Judges ch.2), but that is not Judaism - it's the abandonment of Judaism.

Answer 2

Dictionaries define "Judaism" as The monotheistic religion of the Jews, since the founding principle of Judaism was and is the belief in One God, creator of the universe. This was the teaching which was spread by Abraham, and has continued since then. From Judaism, belief in One God has spread through the Western world.

• Link: A biography of Abraham
  

Jews have always worshiped the One God. Abraham worshiped "the Lord God of Heaven and Earth" (Genesis 14:22 and 24:3) and complained about the Philistines' lack of fear of God (Genesis 20:11).

Jacob confiscated the idolatrous images taken from Shechem (Genesis 35:2) and got rid of them (Genesis 35:4); and refrained from invoking the gods of Nahor (Genesis 31:53). Rachel pilfered Laban's statue-images (Genesis 31:19) in order to prevent him from idolatry (Rashi commentary, ibid.). Joseph placed his hope in the God of the Forefathers (Genesis 50:24).

At the time of the Exodus, God wrecked the Egyptian idols (Exodus 12:12) and warned against idolatry (Exodus 22:19). Later, Moses characterized the Golden Calf as "a great sin" (Exodus 32:21, 30) and punished the worshipers (Exodus ch.32). During the rest of his lifetime and that of Joshua (Judges 2:7), no incidents of Israelite idolatry were reported.

Shortly before he died, Moses warned the people that he suspected that they would eventually succumb to the lure of the idols (Deuteronomy 29:17). Joshua gave a similar warning (Joshua ch.24).
These warnings came true. Many of the Israelites went astray after the foreign gods (Judges 2:11). However, they never invented their own idol. It was always the baneful influence of other peoples. And there were times when the entire Israelite nation repented (Judges 2:1-4) and prayed to God (Judges 3:9, 3:15, 6:6, 10:10). Those who did sin did not represent or influence normative Judaism, just as the later Sadducees and Essenes did not. They were deviating from the Torah's standard; they were publicly, repeatedly, and scathingly excoriated by the prophets, and they caused God's retribution to come upon the entire people (2 Kings ch.17).

• Link: The prophets
  

Because of the idol-worship that did happen, ancient images of idols have been found in Israel too. Images of God aren't found because it is forbidden to represent Him through imagery (Deuteronomy 4:15-16).

It should be noted that idolatry was never universalamong the Israelites. The belief in One God was continued in every generation, whether by the few or the many; and it is those who handed down that tradition whose beliefs we Jews continue today.

Deborah ascribed victory to God (Judges 4:14), Gideon tore down the idolatrous altar (Judges 6:25-27); Samson prayed to God (Judges 16:28), as did Hannah (1 Samuel 1:11) and Samuel (ibid. 12:18); Eli blessed in the name of God (1 Samuel 2:20), Saul built an altar to God (1 Samuel 14:35); Jonathan ascribed victory to God (1 Samuel 14:12), as did David (1 Samuel 17:46); and Solomon built the Temple for God (1 Kings 8:20). A number of the kings "did what was right in God's eyes": David (1 Kings 15:5), Solomon (see 1 Kings 3:3), Asa (1 Kings 15:11), Yehoshaphat (1 Kings 22:43), Yehu (2 Kings 10:30), Yehoash (2 Kings 12:3), Amatziah (2 Kings 14:3), Azariah (2 Kings 15:3), Yotam (2 Kings 15:34), Hizkiah (2 Kings 18:3), and Josiah (2 Kings 22:2). Part of this righteousness was their destroying whatever idolatrous incursions had occurred among the populace (1 Samuel 7:3-4, 2 Chronicles 15:8, 2 Chronicles 17:6, 2 Kings 18:4).

Even at the height of the unfortunate spread of idolatry among the less-loyal Ten Tribes, there were thousands who remained loyal to God (1 Kings 19:18).
And, of course, the Prophets, who spoke in the name of God and warned against idolatry: Isaiah, Jeremiah, Ezekiel, Hosea and so on.
The later sages of the Talmud, who ridiculed idolatry (Megillah 25b), were simply continuing in the tradition of the Prophets whose verses are quoted in that context (ibid.).

See also the other Related Links. Link: Reliability of the Hebrew Bible

• Link: What do Jews believe God is like?
  

More information:

While no excuse should be made for those Israelites who strayed, the following may at least clarify the topic a little.

1) The ancients were tested by a powerful lure towards idolatry. We don't understand it because conditions have changed (Talmud, Yoma 69b).
2) Most Israelites (if not all) who committed idolatry didn't completely forget about their One God. They introduced idols into the picture.
3) It was thought that each nation has its own god. They thought that they needed to propitiate the gods of the nations around them so that those gods "wouldn't give military victory" to those nations over the land of Israel.
4) They figured that they would acknowledge other gods "just in case," and that it would be no worse than someone today who carries a "lucky" penny or rabbit's foot.
Link: What happened with the Golden Calf?