ANYONE WITH a passing familiarity with politics understands that interest groups support and contribute to candidates as a means of advancing their agendas. As far as we know, the only place in the United States where that arrangement has been turned on its head is Montgomery County, where one particular lobby — the local teachers union — wields such outsize influence that politicians shower it with money in return for its support.

Under this ethically perverse setup, state and local elected officials essentially outsource their campaigns — mailings, fliers, even polling — to a single lobbying group. The result is that, once in office, they are beholden to the union and incapable of balancing their support for teachers against potentially competing interests.

The union, known as the Montgomery County Education Association (MCEA), pulled off this trick in both 2006 and 2010, shaking down candidates for the state legislature and county council to the tune of $6,000 each, the limit for campaign donations under Maryland law. A few candidates declined, triggering venomous reactions from the union. Some swallowed their indignation for fear of giving offense. Others went along willingly, noting the union was offering more bang for their campaign bucks than candidates could achieve on their own.

This is an election year in Maryland, so we asked an MCEA official whether the union would again be demanding cash on the barrelhead from candidates in return for its endorsements. The official wouldn’t say. Several officeholders we interviewed were less reticent, although they were wary of being quoted by name, lest they incur the union’s’ wrath. “A lot of us have gagged on this in the past,” said one incumbent. “It’s outrageous and bullying behavior.”

No one disputes that Montgomery has some of the best schools in the nation or that the county’s teachers are treasured for their tough and critically important work. But no other teachers union in Maryland, or elsewhere as far as we know, has conducted itself with the MCEA’s combination of arrogance and ethical myopia. Nor has the union explained why it cannot campaign for its favored candidates as other unions do, on the strength of their members’ financial contributions.

The degree to which elected officials have come to rely on the union — not just for its support but also for bread-and-butter campaign functions such as mailings — has given rise to toxic political pandering that does not serve the public interest. A prime example occurred in 2012, when state lawmakers, bowing to union demands, made it all but impossible for localities ever to cut school funding — even if a recession follows years of outsize budget growth in good times. The result is that Montgomery officials, loath to lock in per-pupil increases in perpetuity, are now reluctant to exceed state-mandated minimums, even in a buoyant economy. This serves no one’s interests.

It is unhealthy when elected officials are so far in the pocket of a single interest group that they are actually in the business of lining it. Let’s hope that a modicum of balance is restored in 2014.