Walter undergoes the most drastic transformation from the beginning to the end of the play. As the surviving male adult in the Younger family, there are expectations placed upon his character that he continually falls short of. This doesn’t mean he’s lost hope, however, and throughout the play he dreams of ways to bring his life and family out of poverty. Trouble is, his judgment is really bad. Although he makes some bad decisions, what redeems Walter is his rejection of Karl Lindner’s offer. His stand for principle over money is celebrated in the play and makes him the protagonist.
Although Lena (known as Mama) may at first glance be more of a guide/mentor, her character also gets protagonist status because of her self-direction and independent thinking. Well, not too independent. Mama continually has her family’s best interests at heart, but that doesn’t exclude her from having an agenda that gets fulfilled. She buys a home for her family without consulting them, but they’re obviously not about to ask her to take it back. It’s her dream, above all others, that gets fulfilled, so we think she deserves protagonist status.