(CNN) FBI Director James Comey's letter to Congress Friday alerting the world to the possibility of new emails in the investigation of Hillary Clinton's private email server certainly has upended the presidential race.

One question now: By doing so, did Comey violate federal law? Specifically the Hatch Act, a 1939 law intended to keep federal employees from directly supporting candidates. Senate Minority Leader Harry Reid suggests he may have, as detailed in a Sunday night letter to Comey

Here's CNN's guide to the Hatch Act, what it prohibits, and how it is usually enforced.

What is the Hatch Act?

Congress passed the Hatch Act in response to concerns that federal employees had been used to support candidates during the 1938 congressional elections. Its general intent is to greatly restrict the ability of most federal employees to engage in political campaign activities (such as soliciting campaign donations or actively working on behalf of individual candidates), especially while on the job -- or to otherwise "use [their] official authority or influence for the purpose of interfering with or affecting the result of an election."

And as its text suggests, the law does not require that the employee's wrongful conduct actually interfere with or affect the result of an election.

Of course, laws that restrict speech will often implicate the First Amendment. But the Supreme Court has twice rejected First Amendment challenges to the Hatch Act, and it has, more recently, taken a narrower view of the First Amendment rights of government employees -- especially when speaking in their official capacity.

And although the law is 77 years old, it has been repeatedly amended by Congress, most recently in 2012 to, among other things, clarify the available penalties for violations of the Act and allow a broader class of employees to run for political office without resigning.

How is it enforced?

The Hatch Act is actually enforced on a fairly routine basis -- albeit usually in cases that do not attract the same kind of national headlines. Typical violations result in disciplinary action -- including suspensions, fines, demotions, duty restrictions, or, in especially serious cases, termination.

But violators aren't going to jail: the Hatch Act is not a criminal statute. Instead, it is an administrative constraint on government employees. The law is enforced by a special independent federal agency -- the Office of Special Counsel -- which is charged with investigating complaint allegations and, where found to be meritorious, either pursuing a settlement with the offending employee or prosecuting their case before the federal agency that oversees internal employment disputes -- the Merit Systems Protection Board. And for presidential appointees like Comey, the Office of Special Counsel submits a report of its findings along with the employee's response to the President, who makes a decision on whether discipline is warranted.

Finally, in addition to the Hatch Act itself, numerous federal agencies have issued their own guidance to employees about how to avoid Hatch Act violations, especially in the run-up to presidential elections.

Thus, as relevant in the case with FBI chief Comey, the Justice Department issued a memo in March 2016 (like similar memos in previous election years), emphasizing that employees "should be particularly mindful of these rules in an election year," and defining prohibited political activity to include all "activity directed toward the success or failure of a political party, candidate for partisan political office, or partisan political group."

Did Director Comey's letter to Congress violate the Hatch Act?

The Hatch Act provision most commonly invoked in discussions of Comey's letter is 5 U.S.C. § 7323(a)(1), which prohibits a government employee from "us[ing] his official authority or influence for the purpose of interfering with or affecting the result of an election."

The key text is the emphasized phrase -- which conditions a violation of the statute on whether the employee's purpose was to interfere with or affect the result of an election. Thus, the Hatch Act does not focus on the effect of the employee's conduct, but the intent. To that end, if Comey did not intend to interfere with or affect the upcoming election through his letter to Congress, then he did not violate the letter of the Hatch Act.

Of course, only Comey knows what his intent was. But Richard W. Painter, the chief White House ethics lawyer from 2005-07 (during the George W. Bush Administration), argued in a New York Times op-ed on Sunday that Comey's intent can be inferred from the absence of a good reason for sending the letter.

"Absent extraordinary circumstances that might justify it, a public communication about a pending F.B.I. investigation involving a candidate that is made on the eve of an election is . . . very likely to be a violation of the Hatch Act and a misuse of an official position," Painter wrote.

And Senate Minority Leader Harry Reid invoked the Hatch Act in a letter to Sunday night. "I am writing to inform you that my office has determined that these actions may violate the Hatch Act," Reid wrote. "Through your partisan actions, you may have broken the law."

Painter on Saturday formally filed a complaint with Office of Special Counsel -- and with the Office of Government Ethics -- seeking to trigger an investigation of Comey's conduct. Whether those complaints have any traction remain to be seen -- but even if they do, there is no scenario in which they will be resolved by Election Day.

If he did not violate the Hatch Act, did Comey do anything wrong?

Even if the FBI director's conduct did not violate the letter of the Hatch Act, it may well have violated the spirit of the Act. After all, the animating purpose of the law is to minimize the ability of individual government employees to use their office in a manner that influences the electoral process.

Some have argued that it would have been just as problematic for Comey to not disclose the existence of the new e-mails before the election. But when faced with such a dilemma, the Hatch Act is best understood as requiring the relevant government employee to balance the importance of the disclosure to pre-election public discourse against its potential prejudice.

In this case, where Comey communicated with Congress knowing that none of the e-mails were to or from Secretary Clinton, is difficult to understand the argument that the value to public discourse outweighed the potential prejudice to Clinton.

That calculus could well have been different if the e-mails contained information tending to incriminate (or exculpate) Clinton, but Comey had no way of knowing whether they did at the time of his communication -- and, at least so far, they appear not to do either.

All the while, Comey's letter has inflamed public passions -- and reinvigorated the public debate -- over Clinton's e-mail scandal, a matter that, even with no substance, can only redound to the detriment of Clinton and the benefit of Donald Trump.

Finally, even if Comey's actions were consistent with the Hatch Act, there is the separate matter of federal ethics rules, and the broader claim that Comey has abused his power in his various public statements concerning the e-mail scandal -- including his public statement and press conference in July announcing that he would not be pursuing charges against Clinton.

Can Comey be fired for his conduct?

Formally, the Hatch Act does authorize the termination of the relevant federal employee as a penalty for an especially egregious violation of the law. But as noted above, absent some evidence of Comey's purpose, it will be difficult for the Office of Special Counsel to establish a violation—or for the Merit Systems Protection Board to order his removal.

But unlike most federal employees, the director of the FBI serves at the pleasure of the President (and for no more than 10 years). Although Comey's term will not expire until September 2023, nothing prevents President Barack Obama (or his successor) from terminating him.

And although the President does not need a reason to fire an employee who serves at his pleasure, it is quite possible that this latest episode will provide one, at least once the 2016 election is over.

If, that is, it ever ends.

Steve Vladeck is a CNN contributor and professor of law at the University of Texas School of Law.