Dueling TV ads are expected to appear this weekend as the clock winds down on the $15 minimum wage referendum on Portland’s ballot.

Opponents of the proposal to increase the minimum wage in Portland to $15 an hour exceeded their informal fundraising goal of $100,000, helped by a large donation from the Portland Regional Chamber of Commerce.

The chamber donated $50,000 of the $123,450 that the “Too Far, Too Fast” political action committee had raised through Wednesday. Based on its campaign filing with the city, the PAC has spent more than $71,000 of that, mostly on web adverting, cable television spot purchases and production costs.

Besides the chamber, which helped form the PAC, major donors include restaurant and retail groups and individual businesses.

Proponents of the measure, which would set the minimum wage at $15 an hour within two years for large business and within four years for smaller businesses, did not form a PAC because donations and expenditures didn’t meet the $1,500 limit for reporting, said Mako Bates, a spokesman for the group. The effort to get the measure on the Nov. 3 ballot was led by the Portland Green Independent Committee.

Bates said supporters produced some yard signs, and members of the Green party will go door-to-door in the city this weekend, urging voters to pass the increase.

The minimum hourly wage in Portland is now $7.50, under state law. The Portland City Council has passed an increase to $10.10 an hour, effective Jan. 1.

An independent group, called Patriotic Millionaires, said this week that it is airing an ad on local stations and the web, supporting an increase in the minimum wage to $15 an hour. The ad features members of the group saying higher wages would help workers support their families and boost the economy, although it doesn’t mention the Portland referendum. The group says its members all earn more than $1 million a year and/or have assets of more than $5 million. The organization generally supports progressive causes and advocates higher taxes on the rich.

Justin Strekal, a spokesman for the group, said the ad represents the first time the organization has weighed in on a local issue.

Chris Hall, the chief executive officer of the Portland Regional Chamber, said he is pleased with the “Too Fast, Too Far” group’s backing by business groups in the city.

In addition to the web and cable television advertising, he said, the group bought time on local radio stations for spots to begin Friday, and might air ads on local TV stations over the weekend.

Hall dismissed the impact of the millionaires’ ad, saying Portlanders aren’t likely to be swayed on a local issue by an outside group.

“You don’t bring in people from away to tell Maine voters what to do,” he said. “It may be too little, too late.”