Former President Barack Obama and Sen. Elizabeth Warren. (Photos: Charles Rex Arbogast/AP, Steven Senne/AP)

Massachusetts Sen. Elizabeth Warren said Thursday that she’s troubled by former President Barack Obama’s accepting a $400,000 speaking fee from a Wall Street firm.

“Well, I was troubled by that,” said Warren when asked about the fee in an interview on “Alter Family Politics” on SiriusXM’s Radio Andy. “One of the things I talk about in the book is the influence of money — I describe it as a snake that slithers through Washington — and that it shows up in so many different ways here in Washington.”

Obama accepted a $400,000 fee from the investment bank Cantor Fitzgerald to speak at a health care conference in September. The former president has been criticized by some on the left for accepting the speaking fee, criticism his spokesperson Eric Schultz rebutted in a statement issued Wednesday.

“With regard to this or any speech involving Wall Street sponsors,” said Schultz, “I’d just point out that in 2008, Barack Obama raised more money from Wall Street than any candidate in history — and still went on to successfully pass and implement the toughest reforms on Wall Street since FDR.”

Warren was promoting her new book, “The Fight Is Our Fight: The Battle to Save America’s Middle Class,” a tour that has led some to speculate she is beginning her candidacy for the 2020 election.

“I’m running in 2018 for senator from Massachusetts,” said Warren when asked by NBC News if the media tour was the prelude to a presidential run. “I am deeply blessed that the people from the Commonwealth sent me to Washington to fight for them, and that’s what I’ll keep on doing.”

Read more from Yahoo News: