Over the years, the outcome of the country’s presidential election has often hinged on the votes of those not formally affiliated with the two major parties and those who, though registered in one party, choose to vote for the other party’s candidate on election day. This, among other reasons, highlights one of the particular benefits of the New Hampshire primary in the long run-up to the presidential general election, because the primary offers the parties their first chance to gauge not only who might appeal to their core base of committed party voters, but also who might energize and attract independent voters and those who might be enticed to cross party lines.

This results from state law — which allows those registered voters who haven’t declared a major party affiliation to pick a party at the polls on primary day, vote in that party’s primary and, if desired, revert to undeclared status immediately afterward. The law also allows a voter registered as a Republican or Democrat to change that affiliation or switch to undeclared status, but only in advance of the primary. And thus an important date looms for currently registered voters who may want to switch parties or preserve flexibility on primary day.

This Friday, Oct. 25, is the last day for voters currently registered as Republicans or Democrats to change their party registration or opt for undeclared status. The cutoff is required to be the Friday before the beginning of the period when candidates can officially file to compete in the primary. That filing period opens on Oct. 30 — given the many candidates who’ve been visiting the state for months now, who knew none has yet officially filed to run? — so by law this Friday is the cutoff date.

Those registered voters who want to stick with their current major party registration or who are undeclared need take no action before this week’s cutoff date. The former will be locked in to voting in their party’s primary, and undeclared registered voters will remain able to do a “drive-by” registration for one of the party primaries on primary day.

Similarly, those who haven’t yet registered to vote in New Hampshire by this Friday’s cutoff or who will need to re-register to vote because they moved after the cutoff into a new town are unaffected by this week’s deadline, as they can either register with a party or elect undeclared status when registering or re-registering to vote before or at the polls.

But if you are registered with a Republican or Democratic Party affiliation and want to change it to the other party — or if, despite current party affiliation, you want to preserve the option to pick your party primary at the polls in February — now’s the time to act.

If you aren’t sure whether you have the party affiliation you want or whether you are undeclared, you can look up your status on the secretary of state’s website at http://sos.nh.gov/voteinforlook.aspx. Or contact or visit your city or town clerk to find out information about how to go about changing your party registration status before Friday’s cutoff.