William Galvin showed leadership last week when he offered to reject help from shadowy outside groups in the Democratic primary for secretary of state if his opponent made the same promise, setting an example and elevating campaign finance to the prominence it deserves.

Considering the sensitive duties of the secretary’s office — which, among other tasks, regulates securities, helps oversee campaign finance, and registers Beacon Hill lobbyists — Galvin’s opponent, Josh Zakim, should have followed suit. Unfortunately, he didn’t. Zakim’s unwillingness to disavow outside spending on his behalf, and his campaign’s dismissal of Galvin’s pledge as an “empty gesture,’’ are discouraging signs.

With the Sept. 4 primary approaching, campaign finance has emerged as a flashpoint — and Zakim isn’t the only candidate who needs to do better.

In the contentious and crowded Democratic primary race for the Third Congressional District seat, state Senator Barbara L’Italien has loaned about $70,000 to her campaign, some of which came from a previously undisclosed “joint family checking account’’ whose other owners are unknown.

Her campaign spokesman said L’Italien is only trying to compete with a male candidates who have an “easy time tapping wealthy networks for campaign funds.’’ (Left unmentioned was that she’s also competing against four other women.) Her spokesperson said the campaign will file an amended disclosure form, but in theory that could happen after the primary. There’s no need to wait. Her campaign could easily assuage concerns by quickly clarifying with whom L’Italien shared the joint account and where the money is coming from.

After all, Massachusetts candidates have set high standards for themselves in the past. Six years ago, Senator Scott Brown and then-challenger Elizabeth Warren agreed to — and then abided by — the “People’s Pledge’’ to discourage outside spending in their closely fought race. Far from an empty gesture, that experiment put the lie to the claim that candidates can’t control outside spending on their behalf. And voters respond when candidates take campaign-finance issues seriously: In upcoming midterm elections in places like Texas and Minnesota, congressional candidates who have rejected money from political action committees are gaining ground.

Unfortunately, in Massachusetts a new pattern has taken hold, with dark-money outfits waiting until the closing days of the campaign to flood the airwaves with attack ads.

When challenged to match Galvin’s pledge, Zakim faulted his opponent for collecting campaign contributions from employees. That’s changing the subject. Zakim wants voters to trust him with an office that sometimes butts heads with lobbyists and special interests. What better way to show he has the independence for the job than by making clear that he doesn’t want them — or anyone else — exploiting campaign-finance loopholes to help elect him?