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.
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