They are almost identical in the context of placing restrictions on rights. They are both rights in my opinion, and if it's not unconstitutional to have requirements to vote such as ID, it's not unconstitutional to have requirements on firearms either. Any American legal to do either of those things are not being denied their right to them.
Article 4
Section 4
The United States shall guarantee to every State in this Union a Republican
Form of Government, and shall protect each of them against Invasion; and on
Application of the Legislature, or of the Executive (when the Legislature
cannot be convened) against domestic Violence.
Republican form of government means a government 'of the people / by the people' where people vote for their representatives. By guaranteeing such government, they guarantee the people the right to vote.