It probably seems unnecessary to note that Karl Rove’s attack operation, Crossroads GPS, routinely lies to the public. As the kids say, “Duh.”

But the problem is, if we simply take Crossroads GPS’ dishonesty as a given and move on, the lies start to gain a certain acceptance. The outfit’s reputation for lying isn’t solidified because it’s not reinforced. It may even encourage more lies since Rove & Co. are facing insufficient pushback.

So, in the interests of the larger discourse, let’s note the latest Crossroads GPS attack ad, which says the Obama administration gave labor special waivers, exempting them from Affordable Care Act mandates, as “a political favor.” The ad goes on to say, “If unions don’t have to comply with Obamacare, why should we?”

In reality, Crossroads GPS is lying.

We spent a good bit of time looking into this claim, because it’s based on some very wonky details of the new health care law, things like annual benefit limits, phase-ins to 2014 and rules advertised in the Federal Register. We’re going to explain all those details momentarily, but we’ll start by giving you the bottom line: Unions do have to obey the mandates of the health care law like any other organization. And if there’s concrete evidence that they’re getting special treatment, we didn’t find it. […]

In ruling on this statement, we understand that the Obama administration would hardly admit to it if it were giving unions special treatment. But looking at the numbers of waivers that have been given to both union and non-union groups, we don’t see any pattern that would support a case for special treatment. The number of waivers are a small sample of all health plans, and many more waivers were given to big companies and corporations. We looked for additional information or evidence on this point and didn’t find it.

But there are additional problems with the ad. The ad doesn’t mention that the waivers only apply to annual coverage limits, that they’re intended to be in place only until 2014 and that many for-profit companies have received the same waivers. It gives the impression that unions are entirely exempt from the health care law, which they are not.

Because the ad gives the impression that unions are exempt from the entire law, and because its evidence for special treatment is so thin, we rate this claim Pants on Fire.

To be sure, this isn’t exactly new. During the midterm campaigns, Crossroads GPS, backed by massive unreported donations, invested heavily in ads that weren’t even close to being true. We’re talking about flagrant, shameless lies.

There are no consequences, of course. Voters see the claims, but not the fact-checking of the claims, so the public has no idea they’re being lied to. The media continues to treat Rove and other Crossroads officials as credible member of the political establishment, and news outlets continue to run the ads, unconcerned with their accuracy.

And when they work, and the targeted candidate loses, it only encourages Rove and his ilk to repeat the pattern, investing additional millions in still more lies.

The discourse deteriorates, the political process gets worse, powerful interests gain more control, and unworthy candidates are put in positions of power.

This is why we can’t have nice things.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.