In all of the end-of-year reviews, the most surprising (and most disappointing) realization for many is what's missing from the list: the charging of Donald Trump.

Indeed, much like Mark Twain, President Trump could claim reports of his impending indictment have been much exaggerated. Even before he took the oath of office, commentators predicted indictment or impeachment as the inevitable end for the 45th president. While 2018 (and special counsel Robert Mueller) could still bring new evidence or allegations, a review of the "clear" crimes articulated over the year have produced little in terms of actual charges.

Collusion

The year began poorly. with a mantra on networks like CNN and MSNBC that Trump and his family were guilty of the crime of "collusion." While a few of us repeatedly noted that there is no crime of collusion with the Russians, the media continued for months to hype the notion that receiving information from Russian sources was a crime. It was not until September that these commentators and hosts began, begrudgingly, to agree that there was no such crime.

Indeed, some liberal outlets by the end of the year acknowledged that it is unlikely that collusion would be the basis for any criminal charge, as opposed to a political embarrassment. What is clear is that the Trump campaign was perfectly willing to accept dirt on Hillary Clinton when Donald Trump Jr., Jared Kushner and Paul Manafort met with a Russian lawyer in Trump Tower. Taking that meeting was remarkably naïve and reckless, but it was not criminal.

Election violations

When challenged on the absence of an actual criminal code provision barring "collusion," many commentators shifted to a novel theory that receiving information would violate the Federal Election Campaign Act as a "thing of value" from a foreign national in connection with a federal election.

Nick Akerman, a former Watergate assistant special prosecutor, declared: "It's illegal campaign contributions. It would be conspiring to commit campaign violations." MSNBC legal analyst Paul Butler declared that the meeting in Trump Tower "is the smoking gun of evidence" of the crime of "soliciting a campaign contribution from a foreign national like a Russian government operative."

The problem is, no court has ever adopted such a broad definition and, if it did, it would raise serious constitutional problems in criminalizing interactions with foreign academics, public interest groups, nongovernment organizations and journalists supplying information to a campaign.

The election-fraud angle has notably subsided recently with revelations that, after long denying any connection to the Russian dossier containing allegations against Trump, the Clinton campaign was forced to admit that it (and the Democratic National Committee) financed the effort by a former British spy to compile that dossier; its information came from foreign entities, reportedly including Russian government sources.

Treason

Sen. Tim Kaine (D-Va.) electrified his base by saying Trump might be charged with treason or impeached for such a crime - even though such a charge is rarely raised without the precursor of a declaration of war. Sen. Richard Blumenthal (D-Conn.) cited his background "as a former prosecutor" to declare that "these emails are a textbook example and evidence of criminal intent" and "potentially" constitute "treason."

Likewise, Richard Painter, chief ethics lawyer for President George W. Bush, has said Trump met "the dictionary definition" of treason. Likewise, former Watergate prosecutor Nick Akerman declared the emails to be "almost a smoking cannon" and added that "there's almost no question this is treason." Treason charges have since receded to the most biased blogs where the line between fact and fantasy is comfortably irrelevant.

Conspiracy

With more defined charges falling to the wayside, some reached for the darling of prosecutors: conspiracy. Cornell Law School Vice Dean Jens David Ohlin has declared the Trump Jr. emails to be "a shocking admission of a criminal conspiracy." MSNBC legal analyst Paul Butler identified the crime as "conspiring with the U.S.'s sworn enemy to take over and subvert our democracy" and "what Donald Trump Jr. is alleged to have done is a federal crime."

Again, this conspiracy theory is based on the simple disclosure that Trump Jr. wanted to see evidence of alleged crimes committed by Hillary Clinton in the campaign from the Russian lawyer.

Alternatively, some have suggested charging Trump with a conspiracy to hack a computer system if the Trump people knew that the Russians were actively hacking into Clinton or DNC computers. Of course, after spending millions of dollars and more than a year of investigation, charging a conspiracy to hack a computer would be like mounting a guppy in your trophy room. More important, after a year of multiple investigations (and endless leaks), there is no evidence of any coordination or direction to hack a computer system.

Obstruction

The most serious allegation in this investigation was possible obstruction by Trump in firing FBI director James Comey. As I have previously discussed, I supported the appointment of a special counsel in light of the firing and the need for an independent investigation into the troubling claims made by Comey. However, I stated (and remain convinced, as 2017 ends) that the available evidence falls well short of a strong case of criminal obstruction.

Nevertheless, former Watergate prosecutor Akerman declared in June (based solely on the evidence of the firing and Comey's statements): "Our president is guilty of obstruction of justice for endeavoring to obstruct an FBI investigation."

While I do not agree with those claiming that a president is immune from an obstruction charge in using his constitutional authority to fire a director, such a charge requires evidence of an intent to obstruct a grand jury or other pending proceeding. FBI investigations are not generally considered a pending proceeding. Again, this claim would allow the government to broaden the element of trying to "corruptly" influence to an extent never reached in any prior case. Trump had ample reason to fire Comey separate from the investigation, and Comey said Trump agreed that the Russian investigation should be allowed to reach an independent conclusion.

Despite this record, many continue to add new criminal acts to this pile. Just last week, Jill Wine-Banks, a former Watergate prosecutor, told MSNBC that Trump's recent tweets criticizing the FBI and the investigation constitute new evidence of crimes. According to Wine-Banks, a president declaring his innocence, or denouncing charges as politically motivated, constitute "obstruction of justice, witness intimidation - and it's obstructing justice." She insisted that Trump was really "saying to agents, 'You better not dig too deep, you better not find anything, because I will attack you.' "

Of course, there were no calls for criminal charges when the Clintons were denouncing a "vast right-wing conspiracy" or supported a campaign to discredit Independent Counsel Ken Starr. More importantly, such a charge would not only leave obstruction as virtually limitless in its definition but would contravene a host of constitutional principles.

Looking objectively at the year, the Trump team has lost little ground in any criminal defense. There have been four indictments or pleas. Paul Manafort and his deputy, Richard Gates, were indicted on 12 counts in what is called a "speaking indictment" - an indictment that discussed a variety of suspicious actions not actually charged. Those allegations could later be the subject of a superseding indictment but, conspicuously, did not include any reference to collusion or obstruction claims tied to Trump or his campaign. The guilty plea of George Papadopoulos, a former foreign policy adviser to the Trump campaign, did tangentially touch on the campaign in discussing Russian contacts; however, the crime was false statements made to the FBI, not the crimes proclaimed to be clear and established throughout the year.

The plea of Michael Flynn also dealt with his false statements, not any crime committed by Trump. Of course, we are all waiting to see what Flynn offered to secure a relatively good deal from Mueller. However, the narrative filed with the court again omitted any nexus to the long-discussed crimes involving Trump. These are not the crimes that motivated the opening of the various federal and congressional investigations.

In other words, 2018 is starting not far from where 2017 began: an investigation in search of a crime.

Jonathan Turley is the Shapiro Professor of Public Interest Law at George Washington University. You can follow him on Twitter @JonathanTurley.