
Given the following passage

"Similarly, the federal constitutional initiative allows citizens to put a constitutional amendment to a national vote, if 100,000 voters sign the proposed amendment within 18 months.[note 8] Parliament can supplement the proposed amendment with a counter-proposal, and then voters must indicate a preference on the ballot in case both proposals are accepted. Constitutional amendments, whether introduced by initiative or in Parliament, must be accepted by a double majority of the national popular vote and the cantonal popular votes.[note 9]",

answer the following question. Note that the answer is present within the text.

Question: If a counter-proposal were to be put in place, it would need to be followed up by whom? 

voters
