It suggests that Thurgood Marshall was an important figure in the civil rights movement.
Explanation:
The word <em>champion</em> has two main meanings:
someone who won a sporting contest or other competition;
someone who strongly supports or defends a person or cause.
Here, the word champion is used in its second meaning. Based on its use and the rest of the information from the passage, we can conclude that Thurgood Marshall was an important figure in the civil rights movement.
