share a platform

（the platform） （壇上の）演説者;
share a platform
1 to give speeches or to perform at the same public event:
It was the first time a Green politician and a Labour minister had shared a platform .

2 [C] UK the people who are up on a platform in order to speak to an audience:
An elderly lady stood up and said she had a question for the platform.
The platform party (= the group on the platform) applauded loudly.

(from Cambridge Advanced Learner's Dictionary)