What does “Too much toothpaste has left the tube” mean? Is it a well-received turn of phrase?

Question

I was drawn to the phrase, “Too much toothpaste has left the tube” appearing in Washington Post’s (January 13) article under the title, “Comey should resign.”

“(FBI Director James B.) Comey was in a difficult situation, boxed in by Clinton partisans and heading an agency that allegedly was expressing distrust of the Obama Justice Department. By all accounts, Comey is a decent man and a straight shooter, and it’s unfortunate that the Clinton scandals landed him in such an untenable position. But too much toothpaste has left the tube. The FBI won’t be thought of as being at its best, and the agency’s investigations and actions won’t be met with complete trust, unless there is a change at the very top.”

I often hear the expression, "You cannnot push toothpaste back into the tube," but I've never heard of “too much toothpaste has left the tube.” Does “toothpaste” here represent unsettled problems or suspicions on the stage? Is it a popular turn of phrase, or simply a writer’s coinage? If it is a well-received expression, how can it be used in other contexts?

Answer 1

It is apparently equivalent to "too much water has flown under the bridge" implying too much happened that can't be undone now (in the context of the question: the situation cannot be rectified under the current leadership).

TFD (idioms):

water under the bridge
A past occurrence, especially something unfortunate, that cannot be undone or rectified:
All that is now just water under the bridge.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Answer 2

Toothpaste being squirted out of a tube isn't exactly a common idiom, but it's a common analogy used to teach children about gossip:

To give students a visual reminder about rumors, I used toothpaste. I had students volunteer to squeeze toothpaste out onto a paper plate until the tube was empty. I asked the students what the toothpaste was meant to represent. A student commented, "The toothpaste gets bigger and bigger just like a rumor."
Each time the toothpaste was squeezed out, it represented someone spreading a rumor. When the tube was empty, I asked for another volunteer to put all of the toothpaste back in the tube. Students wanted to try to put the toothpaste back in, but we discussed how it would be impossible to get all of the toothpaste back in. One student shared, "the toothpaste is just like a rumor. Once [a rumor] is out you can't put it back in."source

Here, the idea is that too much damaging information has gotten out for Comey to be able to stick around and be trusted. It's similar to The cat's out of the bag, but with a couple differences:

In the context of the whole editorial, you can tell they don't (at least at this point) believe Comey actually did anything wrong--the problem is that he's surrounded by rumors and suspicion, which will haunt him even if the investigation shows he did everything right ("The toothpaste gets bigger and bigger").

The cat's out of the bag connotes the escape of something you were trying to keep hidden. If they used this phrase here, it would sound like Comey did some specific wrong thing, then tried and failed to cover it up, which they don't think ("By all accounts, Comey is a decent man and a straight shooter").

Also, Too much toothpaste implies that different amounts of "toothpaste" can "leave the tube," i.e maybe Comey would've been fine if less information had become public. With a cat, you just have in vs. out, with no gradation in between.

They may also be trying to cast aspersions on those who suspect Comey of wrongdoing by comparing them to children spreading rumors, but if so that's certainly not the main point.