She seems at ease, sitting on the top step of a large front porch, her legs crossed and a long, slim cigarette between her fingers. She wears a bit too much makeup, perhaps, but her face is pleasant and gives no reason to believe that the ensuing conversation won't be the same.

"So, can you tell me a little about your ex-husband?" I ask, standing on the bottom step with a notepad and pen in hand. Her words start flowing, in a tone that could put a baby to sleep, and for a moment it seems that they may never cease.

"Cheating son of a bitch." "Selfish bastard." And worse. They are in sentences, of course, but all I hear is those phrases. I try to display sympathy and concern, but inside I'm smiling because I know, as I always have, that ex-wives, ex-husbands, ex-girlfriends, ex-lovers, ex-anythings make some of the best sources.

Brian Stauffer

My business partner Alan and I had received the call a few days earlier. A local politician was making noise about jumping into a congressional race against a longtime incumbent who was worried, apparently, about his job. The election was more than a year out, and the potential opponent had not yet announced. The task at hand was to try to make sure that he never did.

We get these projects every now and again. "Just see what's out there," they say, "and if there's nothing, so be it." But of all the different types of campaign research we do, this usually proves the most fruitful: local politicians rattling their chains without having thought through the whole idea—and without understanding that longtime incumbents work hard to remain longtime incumbents.

In this case, the front-porch interview isn't going very far; she just doesn't know that much about the man. His business dealings are a mystery to her. His political affairs are an unknown.

"So when you say he's a 'bastard,' I'm just guessing you're talking about your marriage?"

And then she begins. Yes, she is referring to her marriage. Yes, he was the most ill-tempered husband on the face of the earth. And yes, he had left her and started seeing another, younger, woman. They now live together, she tells me. They travel a lot, go to places he never took her. She resents him for all of it.

"Anything else?"

"Oh yeah," she says, almost as an afterthought, "I think he was arrested for beating her up."

These are the moments when a pause is not only mandatory; it is involuntary. I just stare down at my notepad and jot the words "assault" and "arrested." I scribble a big star to the side.

"So, what was that all about?" I ask in a near monotone, still looking down.

She tells me that the couple was going on a vacation out West when the incident supposedly occurred. She doesn't know where they were going, but says he "slapped her around" at an airport en route. She doesn't have much else. She then asks if it is something I can use. I tell her it's possible but that I'm not sure.

But that isn't true. I am sure.

Polling is the lifeblood of any well-funded political campaign. The information that my business partner Alan and I provide is used to develop the questions that pollsters ask of voters. And one thing polls show is that voters will tolerate an awful lot in politicians—cheating on spouses, dalliances with prostitutes, the occasional DUI. But they will never condone domestic violence.

Back at the office, I'm poring over a map, trying to figure out where the slap-down may have occurred. If such an incident did happen, there could be a report on file at one of the big Western airports. I call each of them, but with only a couple left to go, I'm striking out.

The call to the next airport security office starts the same way the others have. I tell the officer that I'm trying to track down some information on an assault that supposedly occurred at one of their gates. I have the name of the assailant and the victim, and I'm hoping for some assistance.

He asks what it's for. I say, "I'm doing some work for a client who needs to track this information down for a project they're trying to resolve in a hurry." Clear but confusing.

"Who's your client?"

"I'm not at liberty to say."

At this point, if the officer asks for additional details about the incident, you're usually golden. This one asks if I have the date of birth of the man I'm inquiring about. Of course I do. I got it from the ex-wife. Do I have the date this happened? No, just a period of time. Do I know what happened? Uh, no, that's why I'm asking.

He seems somewhat satisfied and asks for my phone number. He's going to do some checking and get back to me. Good, but not guaranteed.

Later, he calls back, excited to share. Yes, there is a report of an assault that occurred in one of the terminals between the ex-husband and the girlfriend. It apparently began with an argument that escalated into the slap-around. There was a busted lip, some blood and a short trip to the carpet for the girlfriend. Although the report makes no reference to an actual arrest, it is better than I had hoped.

Alan and I do not relish the pain or misfortune of victims. If you ask us, a man who's responsible for that kind of abuse should get everything that's coming to him and probably more. But it's not for us to decide. Our job is simply to find, document and collect. In our work, the judges and juries reside in the voting booths and campaign offices.

The client or candidate for whom we work generally has the next move. With a report like the one we've just provided, the scenario might go something like this:

A mutual friend of both the incumbent and his potential opponent makes a visit to the potential opponent and explains that a "situation" has arisen that could cause him some embarrassment. The friend offers a few details about the incident and says that it would probably be better if he considered backing off his intentions of running. At this point, the potential candidate acts surprised and insists that he was not involved in any such incident. He tells the friend that he has every intention of running. His insistence quickly turns to silence when the friend pulls out the incident report and hands it to him.

Within a couple of weeks of passing along the faxed report from airport security, Alan and I get an email telling us that the ex-husband has decided, in so many words, to stay put.

"Did you read this?" I ask Alan, almost in passing.

"Yep. Pretty good," he responds without looking up from his computer.

Nothing more is said.

—Mr. Rejebian is the co-author, with Alan Huffman, of the new book "We're With Nobody: Two Insiders Reveal the Dark Side of American Politics," from which this is excerpted.