In 1907, Chief Justice Charles Evans Hughes, said, “We are under a Constitution, but the Constitution is what the judges say it is.”
There you have a quintessentially view of a Pharisee, someone who both believes in the Torah and who believes its meaning is determined by its interpretive tradition. On the other hand, a Sadducee would simply say, to use Chief Hughes’ terms, “We are under a Constitution.” We don’t need an interpretive tradition for we need only to seek out the original intent.
Pharisees were judicial activists; Sadducees were judicial conservationists.
Consequently, the Pharisees built up a body of interpretive tradition, which today is called the Mishnah and the Tosefta, with an even larger body of anecdotal reflection in the Babylonian Talmud and the Jerusalem Talmud. At the time of Jesus this interpretive tradition was merely oral tradition, but it carried the day.
So, this permits us to see the Pharisees as those who both believed in the Torah but who knew it needed interpretation, applications, and it needed to do so along careful lines of thought and procedure.
If you want to use the terms of today, then the Sadducees were the political conservatives and the Pharisees the political liberals — in the legal sense (both were conservative morally).
Jesus agreed with neither? Where would you put him in the first century legal struggle of “how do we live under the Torah?”