When we think of freedom of speech, the spoken word is usually what comes to mind. But the First Amendment of the federal Constitution (and, hence, Article II, section 7 of Montana’s Constitution) also protect symbolic speech.
Symbolic speech is non-verbal action that clearly conveys a specific message to anyone who sees and reads it. It can take the form of public protests, such as sit-ins and marches, demonstrations, wearing buttons, armbands or clothing items such as t-shirts, nudity, flag-waving, flag-burning, burning draft cards and bras, braille, sign language and even non-criminal actions that others might find offensive (the universal one finger salute), to name a few.
My friend, Alan Nicholson, and I were exchanging emails, and he raised an interesting question: Could the right to vote be an exercise of free speech? I believe that Alan is correct, voting is the exercise of free speech. I suggest that it is a form of symbolic speech.
One commentator put it this way: “Voting is an act of pure expression. It is one of the most consequential expressive acts in a persons’ life, when a voice becomes an action, and those actions dictate how we are governed.” 
Another author states: “It seems like an obvious proposition that a citizen registering to vote or casting a ballot is engaging in free speech, a fundamental right entitled to full protection under the First Amendment to the United States Constitution.” This commentator notes, however, that the US Supreme Court rarely interprets the regulation of voting as it does other regulation of speech—that is, with the most stringent form of review, strict scrutiny, applying robust First Amendment law.  Ironically, this from the Court that determined in Citizens United that money equals speech.
However, keep in mind a fundamental principle of constitutional law: under its own constitution, a state can provide more protection of a right protected under the federal constitution; but a state cannot provide less protection.
With that principle in mind, assume that registering to vote, filling out a ballot (either mailed or at a polling place) and casting that ballot are actions that are, at the very least, forms of symbolic free speech—an expressive non-verbal action that clearly conveys a specific message to anyone who sees and reads it.
Then, add to that the mandates and prohibitions of Montana’s Article II, section 13, which states: “All elections shall be free and open, and no power, civil or military shall at any time interfere to prevent the free exercise of the right of suffrage.” One could hardly craft a stronger protection of the right to vote—a constitutional guarantee that all elections must be free and open and prohibiting any civil power (including the legislature, of course) from interfering to prevent the exercise of this right.
Thus, reading together the rights in Articles II, section 7 (free speech and expression) and section 13 (right of suffrage) it is clear (as Alan also observed) that under Montana constitutional law, the right to vote must be protected with no less rigor than is the right of free speech and expression. That is, that both rights, being fundamental rights, any restrictions on the right to vote must be subjected to free speech strict scrutiny analysis.
To that point, Montana’s right of free speech proclaims, in pertinent part that: “No law shall be passed impairing the freedom of speech or expression.” Voting being a form of speech and expression means that no law shall be passed impairing the right to vote. And the mandates and prohibitions of Article II, section 13 double-down on that point!
There is simply no constitutional basis by which the legislature, the governor or any public official or branch of government can impair or interfere with Montanan’s right of suffrage. “No law shall be passed …”.