Sometimes during lengthy floor debates on bills, interesting things happen in the witching hours. Such was the case late Wednesday, when Representative John Lewis of Georgia pushed back with a fiery speech directed at an amendment offered by Representative Paul C. Broun of Georgia that would have barred the Justice Department from using money to enforce a part of the Voting Rights Act. At around 10 p.m., Mr. Lewis, a former civil rights leader, took to the podium to denounce the amendment, which sought to end financing for enforcement of Section 5 of the Voting Rights Act, designed to protect minority voters from being disenfranchised.