What does Mr Ewell mean by one down two more to go in To Kill A Mockingbird?

Although it was never clearly stated, it is assumed that Mr. Ewell was referring to getting revenge on Atticus and Judge Taylor, because although he won the court case, he feels they made a fool of him. This is assumed because later in the book, Mr. Ewell spits on Atticus, breaks into Judge Taylor's house, and tries to kill Scout and Jem.