Broadband internet has emerged as the most divisive issue in the campaign for mayor of Seattle, the largest city in the Pacific northwest of the United States.

The incumbent, Mike McGinn, is a longtime supporter of the “SeaFi” broadband initiative, a public-private partnership to make use of 500 miles of unused fiber lines that were installed throughout the city during the last dot-com boom. That could provide very fast, “gigabit” internet to much of Seattle through a private company.

Comcast, one of the city’s major providers of broadband internet, isn’t happy with the steep competition that SeaFi poses. The company is pouring money into the campaign of McGinn’s opponent, senator Ed Murray. Comcast’s contributions though a variety of political action committees have so far totaled more than $70,000.

Murray says he will honor the existing pilot agreement for SeaFi, but hasn’t committed to future expansion. McGinn, on the other hand, has made the program a hallmark of his tenure and hopes to expand it.

In an “Ask Me Anything” online discussion with the Reddit community recently, McGinn noted that “Comcast gave Murray a big pile of money.” He encouraged commenters on the site, who are famously critical of cable companies like Comcast, to help spread the word about the company’s support of his opponent.

The race, which ends on November 5, remains tight, according to recent polls of Seattle voters.