Hillary Clinton (Melina Mara/The Washington Post)

CBS's Scott Pelley interviewed Hillary Clinton on Thursday night. One exchange tells you everything you need to know about Clinton's struggles in the Democratic primary race so far and why she continues to be dogged by questions about her honesty and trustworthiness. Here it is:

PELLEY: You know, in ’76, Jimmy Carter famously said, “I will not lie to you.”

CLINTON: Well, I have to tell you I have tried in every way I know how literally from my years as a young lawyer all the way through my time as secretary of state to level with the American people.

PELLEY: You talk about leveling with the American people. Have you always told the truth?

CLINTON: I’ve always tried to. Always. Always.

PELLEY: Some people are gonna call that wiggle room that you just gave yourself.

CLINTON: Well, no, I’ve always tried —

PELLEY: I mean, Jimmy Carter said, “I will never lie to you.”

CLINTON: Well, but, you know, you’re asking me to say, “Have I ever?” I don’t believe I ever have. I don’t believe I ever have. I don’t believe I ever will. I’m gonna do the best I can to level with the American people.

I mean, what? W-H-A-T?  "I've always tried to" tell the truth?  On what planet is this a good answer for a politician?

The answer, of course, is on no planet. While I am less familiar with politics on Mars than I am with those on Earth, I am pretty sure that being unable to simply say, "Yes, I have always been truthful with the public," would be a problem on the Red Planet, too.

This a double whammy of bad for Clinton.

First, it does nothing at all to quell concerns about her ability to be honest and straightforward. In the New Hampshire exit poll, more than one in three (34 percent) of all Democratic primary voters said that honesty was the most important trait in their decision on which candidate to support. Of that bloc, Bernie Sanders won 92 percent of their votes as compared to just 6 percent for Clinton.

That's broadly in keeping with national polling over the last year, which has consistently shown large majorities of voters voicing skepticism about Clinton's trustworthiness. Her answer to that criticism has, to date, been to blame it on a Republican Party obsessed with her and willing to say or do anything to tarnish her reputation. There's truth in that, but, as the New Hampshire exit numbers suggest, the problem is bigger than just Republicans out to get her.

Once considered a firewall for Hillary Clinton, Nevada has sharply turned into a tight and unpredictable contest for the former secretary of state as senator Bernie Sanders steadily gains support from critical voting blocs. (Alice Li/The Washington Post)

Second, the answer from Clinton on honesty reinforces a perception that the former secretary of state tries to play with words, giving a heavily couched response when a simple one would — and should — do. You can imagine people rolling their eyes or saying, "Why doesn't she just answer the question?" while watching that painful response by Clinton.

I think I understand why she answered the way she did. She knows she has been in public life for a long time and that she has said lots and lots of things. Because of that, it's possible that at some point in the future, someone will unearth a statement in which it could be construed that she wasn't telling the whole truth. Clinton is protecting against the damage incurred by such a revelation.

But when you have the problems regarding honesty and trustworthiness that Clinton does, the only right answer to Pelley's question is: "Yes, I have always been truthful. Of course." That Clinton didn't give that simple answer suggests she is either (a) unaware of or doubts the depth of voters' concerns with her ability to be honest, or (b) she is so naturally cautious as to get herself in trouble even on a question she has to know is coming.

Either way, Clinton just made things harder for herself with that answer to Pelley.