challenging protesters to deny their presence in the chamber

challenging protesters to deny their presence in the chamber = challenging protesters who denied their presence in the chamber?

Context:

Speaker Reed remained firm in the face of this parliamentary tumult and angry debate. He continued to count nonvoting legislators for quorum purposes, challenging protesters to deny their presence in the chamber. Reed even ordered the doors of the chamber locked when Democrats tried to exit; instead, Democrats began hiding under their desks, which left Reed undeterred in counting them. Finally, after five days of stridency, the contested election case was taken up and Republican Smith emerged the victor by a vote of 166 yeas, 0 nays, and 162 not voting. Then, on February 6, 1890, the Reed-led Rules Committee reported a new set of House rules. One of the new rules—Rule 15—established a new procedure for determining quorums (counting lawmakers in the chamber who had voted as well as those who did not vote).

More:

http://en.wikipedia.org/wiki/Disappearing_quorum#Disappearing_quorum