There are at least three ongoing investigations into Democratic presidential candidate Hillary Clinton's time as Secretary of State. Here's an explanation of who is investigating, and why. (Gillian Brockell/The Washington Post)

By my count, this latest State Department inquiry makes for three active investigations by the federal government that touch directly or indirectly on the 2016 Democratic presidential front-runner.

1. The newly revealed State inquiry into the Clinton Foundation and top Clinton aide Huma Abedin

Huma Abedin has stuck by Hillary Rodham Clinton since she interned for her in the first lady's office. Here's what you need to know about Huma Abedin. (Sarah Parnass/The Washington Post)

2. The ongoing State inquiry into Clinton's private email server

3. The FBI investigation into Clinton's email server

And that list doesn't include the myriad looks Congress is taking into Clinton's time at State.

It's worth noting right at the top here that Clinton herself is not the target of any of these inquiries or investigations. Which from a legal perspective is very important, but which, from a political perspective, is far less convincing.

Democratic presidential candidate Hillary Clinton responded to reporters in Las Vegas Aug. 18, over the controversy surrounding her personal e-mail server. (AP)

Here's why the latest revelation regarding Clinton's time at State is so problematic:

* It furthers the "where there's smoke, there's fire" argument.  This hurts Clinton both coming and going. For Republicans, it hands them yet another way to suggest that something untoward is going on with Clinton. For Democrats, it increases their anxiety about the possibility of nominating someone who could fall under an ethical cloud just as the party is trying to elect them to the White House.

* It makes it increasingly difficult for Clinton, as she has done since the revelation that she had a private email server broke a year ago, to cast the questions raised about her time at State as simply a partisan fishing expedition. "There is a concerted effort to try to make partisan advantage by really trying to throw so much at me that even if little splotches of it stick, it will cloud peoples's judgment of me," Clinton told MSNBC's Rachel Maddow this week. "That is a burden I carry."

There is, without question, a desire on the part of many Republicans to cast Clinton in the worst possible light using almost any means necessary. But it strains credulity to believe that Republicans somehow concocted a way to get the State Department and the FBI to look into Clinton's tenure at State.

Republican presidential candidates like Sen. Ted Cruz and Sen. Marco Rubio are weighing in on the State Department's Jan. 29 announcement that some of the emails sent on former Secretary of State Hillary Clinton's private email server contained top secret information. (Reuters)

As I wrote in this space this week, at some point Clinton will need to directly face down the fact that it's not just Republicans who are talking about her emails or her paid speeches or the Clinton Foundation. The numbers coming out of the New Hampshire exit poll make plain that Democratic voters care about honesty in their politicians, and those that prize it the most are voting heavily against Clinton.

The revelation of another investigation will only further those concerns and worries — at a time when Clinton is trying to face down Bernie Sanders's increasingly robust challenge.  Clinton will almost certainly be asked about the latest State investigation in the debate tonight. How she responds — and whether Sanders or the debate moderators push her on that response — could be a pivot point not just tonight but in the race more generally.

At a debate in Milwaukee, Democratic presidential candidates Bernie Sanders and Hillary Clinton diverged slightly on how they would reform health care and immigration, while largely agreeing on the need for change in policing. (Sarah Parnass/The Washington Post)