Supporters hold a poster during a campaign rally by Democratic presidential candidate Sen. Bernie Sanders on Feb. 14 at Bonanza High School in Las Vegas.  (Ethan Miller/Getty Images)

ELKO, NEV. — Democratic presidential hopeful Bernie Sanders on Friday pledged to release all the transcripts of speeches he has given to Wall Street firms — there are none — in a not-so-subtle poke at his rival Hillary Clinton.

Clinton, the former secretary of state, said during a forum broadcast Thursday night by MSNBC and Telemundo that she would release transcripts of her paid, closed-door speeches to Wall Street firms “when everyone else does.”

“Sen. Sanders accepts Clinton’s challenge,” said Sanders spokesman Michael Briggs. “That’s easy. … So now we hope Secretary Clinton keeps her word and releases the transcripts of her speeches. We hope she agrees that the American people deserve to know what she told Wall Street behind closed doors.”

Once considered a firewall for Hillary Clinton, Nevada has sharply turned into a tight and unpredictable contest for the former secretary of state as senator Bernie Sanders steadily gains support from critical voting blocs. (Alice Li/The Washington Post)

The jab by the Vermont’s senator’s  campaign came on the eve of the Nevada caucuses, a contest that has become unexpectedly close, according to recent polls. Both Clinton and Sanders were maintaining busy campaign schedules in the state on Friday.

Clinton gave numerous paid speeches after leaving her post at the State Department in 2013, including some to financial firms, large corporations and trade groups. Some of those speeches were open to the press, some were not.

On the campaign trail, Sanders has seized on speeches Clinton gave to financial interests, questioning whether they undercut her commitment to ushering in the kind of Wall Street reforms he says are necessary to avoid a repeat of the 2008 financial meltdown.

In its statement Friday, the Sanders campaign noted that Clinton reportedly made $21.7 million on the speaking circuit, including $675,000 for a series of three addresses to the large financial firm Goldman Sachs.