On September 4, the political advertising window opened on Boston television and radio stations.  This is a 60 day period leading up to a general election when broadcast stations licensed by the Federal Communication Commission are obligated to offer candidates for national office the opportunity to buy commercials at the lowest unit rate (LUR).

For example, if a high-frequency advertiser like McDonald's earns the lowest rates on a particular Boston radio station during morning drive-time, then any candidate for federal office must, during the 60-day political window, be offered the same rate for morning drive time on that station, regardless of frequency.

If, however, the McDonald's rate is contingent on the radio station's ability to pre-empt commercials without notice, then qualified candidates must agree to identical terms to receive the same rate.

To facilitate the purchase of commercials on Boston radio, stations will supply candidates with a political rate-card.  This card will show the LUR by time of day and by preemption parameters.

Here are other important facts about political advertising on Boston radio.

There are more than 4.3 million registered voters in the Boston radio metro. Here is the number by county:

• Essex, MA: 533,867
• Middlesex, MA: 1,045,30
• Norfolk, MA: 485,131
• Plymouth, MA: 367,838
• Suffolk, MA: 472,972
• Worcester, MA: 541,824
• Hillsborough, NH: 892,318

According to Nielsen, Boston radio reaches significantly more of these registered voters than all other media, including local television pay-TV, newspaper, social media platforms, and streaming audio sites like Pandora or Spotify.

Many times the difference between winning an election and losing is a handful of ballots. This is true in races for almost every elected office, referendum, and issue on the national, statewide, and local level.

To win a modern election requires advertising. Successful advertising requires reach. In the Boston area, the most potent way to reach voters is on local radio.

The Boston area includes the counties of Essex MA; Middlesex, MA; Norfolk, MA; Plymouth, MA; Suffolk, MA; plus portions of Worcester, MA; and Hillsborough, NH.

Last week, for instance, 90.6% of all registered voters in these counties tuned-in to a Boston radio station.  This is significantly more than were reached by local TV, local newspaper, or the major social media sites like Facebook and Instagram.