One of the senators will lead the group to the front of the capitol.
Note sure if you noticed the presence of 'will' in the above sentence. With 'will', only the base form
of the verb is used. Since you are a native speaker, this would come naturally to you and you do not need to even be aware of this rule.
Without the 'will', what you've stated would be correct:
One of the senators leads the group to the front of the capitol.
GMAT - 99th Pecentile, MBA-ISB
Faculty @ EducationAisle
Read testimonials of our students who made it to top schools (IIMs, ISB, Darden and XLRI, among others): http://EducationAisle.com/testimonials.html
No "kudos" are required if you find this post useful; absorbing this learning and getting a great score would be your best gratitude.