Not long ago, Ms. Selbst disparaged the notion of going into finance, telling The Financial Times that it was an option for “a lot of bored poker players.”

“I’m also anticapitalist at heart,” she added, “so it doesn’t really fit in with my values, I guess.”

Now, she said in an interview, she sees it both as a more stable lifestyle as she and her wife expect their first child in October and as an intellectually stimulating challenge.

But even more than that, Ms. Selbst said, it’s a means to an end, that end being making as much money as she can as quickly as she can to help finance the progressive causes she supports. She has long been an active philanthropist; her charitable foundation, Venture Justice, for instance, pays for a two-year fellowship for a lawyer at the NAACP Legal Defense Fund through a program organized by Equal Justice Works. She has also raised $500,000 for the Urban Justice Center via an annual charity poker tournament and served for a time on that organization’s board.

“Am I going and working with clients in prison? No, but at the end of the day, we’re investing money and we’re making money, and that’s important,” said Ms. Selbst, who earned her law degree in 2012 and worked part time in recent years for a police-misconduct litigation firm. “Hopefully, if I’m good at this and I do well, then that’s probably the most efficient way for me to support the causes that I care about.”

Ms. Selbst’s pivot also reflects her gimlet-eyed view of poker today.

In the early 2000s, she was among the flood of players inspired to play by the 1998 film “Rounders” and the out-of-nowhere $2.5 million World Series of Poker championship win in 2003 by a Tennessee accountant and online player, Chris Moneymaker. (Yes, his real name.) Curious, Ms. Selbst started playing online and built her account up to $150,000 by the time she graduated from Yale with a political science degree.

After graduation, she worked as a management consultant in the New York office of McKinsey & Company, but the cards kept calling her back.