After a bitter internal argument, the NLU endorsed the women's labor movement, which consisted mostly of protective organizations formed to look after women's rights on the job. At the fourth NLU congress, Susan B. Anthony's credentials were challenged and subsequently rejected on the grounds that she had used the Workingwomen's Protective Union as a strike-breaking organization. The NLU continued to seat delegates from women's organizations, but support for those organizations eroded. Nonetheless, the NLU was one of the first labor organizations to advocate equal rights and equal pay for women, even though it remained opposed to women's suffrage. But the national trade unions that were a part of the NLU refused to support equal rights or equal pay for women, and few of them accepted women as members.