SCOTUS just soundly rejected an idea called "independent state legislature theory" in a case called Moore v. Harper. Here's a good summary of the implications if it had been upheld:

"Proponents of the independent state legislature theory reject this traditional reading, insisting that these clauses give state legislatures exclusive and near-absolute power to regulate federal elections. The result? When it comes to federal elections, legislators would be free to violate the state constitution and state courts couldn’t stop them."

https://www.brennancenter.org/our-work/research-reports/independent-state-legislature-theory-explained