BOSTON — With just four weeks to go until the primary, Attorney General Martha Coakley is going on the air with a positive new ad about her gubernatorial candidacy.

The 30 second spot focuses on Coakley's time in office as the attorney general and presents Coakley as a defender of the "little guy."

The ad notes Coakley's 2011 suit against five banks over lending practices and home foreclosures that resulted in a $25 billion settlement spread across 49 states. Massachusetts received $317.9 million as a result of the lawsuit.

Coakley touts her economic plan in the ad with a narrator saying that it "will build an economy that works for everyone."

Her Emily's List endorsement makes an appearance in the ad, too.

The $60,000 ad buy is tiny when compared to the $900,000 in television advertising boosting her chief Democratic rival, Treasurer Steve Grossman. Still, the pro-Grossman advertising, some purchased by the campaign and some by an outside super PAC, does not appear to be helping, as Coakley has maintained a commanding lead in the polls all summer.

A campaign source said that the ad, produced by AKPD, will only air in the Boston market.