Editor's note: Ruben Navarrette Jr. is a CNN.com contributor and a nationally syndicated columnist.
San Diego, California (CNN) -- As Anthony Weiner is about to find out: When you're a politician, not all lies are the same. There's a big difference between breaking a campaign promise by failing to deliver on something and breaking the public's trust with an outright falsehood.
When you do the former, the public will shrug and surmise that you're no better or worse than any other elected official. But when you do the latter, you signal that you can no longer be trusted on any level.
In what you'd have to call a negative trend, Americans have become accustomed over the years to politicians saying one thing to get elected and doing another once they're in office. In fact, these days, people think that is normal. Whether it's George H.W. Bush breaking his promise of "no new taxes," or Barack Obama violating his pledge to make immigration reform a priority of his administration, most people are tolerant of broken promises. They tell themselves that circumstances have changed or that the elected official will eventually make good. Besides, they say, every politician has his share of unfulfilled pledges.
That's not Weiner's problem. The lies he told in response to reporters' questions were much worse and much more direct. They were told not with the desire to get elected but with the intent to mislead and deceive. And that being the case, the damage to his political future is likely to be much more severe.
But you knew that already, if you caught even a glimpse of Monday's news conference where Weiner finally came clean about posting lewd photos on his Twitter account and lying about it.
It was a much different story than what we heard last week, when Weiner claimed that his account had been compromised and that, as a "prank," a hacker had posted a lewd photo on the account and sent the photo to a young woman. In a textbook example of how not to answer a question, Weiner told MSNBC's Luke Russert that, while he didn't send the tweet, he "can't say with certitude" whether he was the person in the photo. In an interview with CNN's Wolf Blitzer, Weiner couldn't even say whether the underpants in the picture were his.
Monday, amid reports that there were more pictures that could yet be released, Weiner apparently decided to cut his losses before the story got worse. He apologized for lying about the ordeal and admitted carrying on inappropriate virtual relationships with several women he'd met online. Better late than never, the married congressman took "full responsibility" for both the relationships and for lying in an attempt to cover them up.
"To be clear, the picture was of me, and I sent it," Weiner said. "I'm deeply sorry for the pain this has caused my wife and our family, my constituents, my friends, my supporters and my staff," he said. "I lied because I was ashamed at what I had done, and I didn't want to get caught."
No kidding. Isn't that why most people lie -- because they're afraid of getting caught? That's obviously no excuse. Nor does it look good that the Democratic leadership in the House wants to know whether Weiner used government resouces while he "exchanged messages and photos of an explicit nature with about six women over the last three years." (Weiner says he doesn't believe he did.)
House Minority Leader Nancy Pelosi announced just moments after the news conference that she would call "for an Ethics Committee investigation to determine whether any official resources were used or any other violation of House rules occurred." Weiner said afterward that he "will fully cooperate with an investigation by the House ethics committee."
Whether or not Wiener violated House ethics rules, it is already clear that he violated the trust of his constituents. When he lied to reporters, he lied to the American people, who count on journalists to tell them what elected officials are doing on their dime. There's no way to make up for that kind of deceit. The relationship between lawmaker and constituent is forever damaged, and this public servant will never be effective again.
As it stands, Weiner is just holding a seat that the people of New York could put to better use. That's why the congressman has no choice but to resign.
The opinions expressed in this commentary are solely those of Ruben Navarrette Jr.