Calls for Trump to be impeached were rife even before he took office, but since he fired FBI Director James Comey, demands for his impeachment have grown increasingly louder. It can't happen at random, though — and in this case, there are several reasons why Trump could be impeached or otherwise removed from office.

According to the Constitution, the reasons for impeachment and removal from office are "treason, bribery, or other high crimes and misdemeanors" — but there's been a lot of debate over what those words actually mean. And for impeachment proceedings to begin, first, the House of Representatives must formally charge the president with one of those crimes, and then the Senate must try him.

Criminal activity aside, it's unlikely Trump could do anything to force his impeachment at this very moment in history. In order for him to be impeached in his first term — especially before the midterms — a Republican-controlled House would have to charge him, and then a Republican-led Senate would have to try him and find him guilty. Given the loyalty to party above country that so many in Washington, D.C. seem to show today, it would take a pretty serious misstep for this Republican Congress to turn on him so completely.

But then again, it's 2017, and it's Trump, so all bets are off. Here are a few of the reasons that impeachment proceedings could actually get started.

1 Obstruction Of Justice Eric Thayer/Getty Images News/Getty Images Removing Comey as FBI Director caused a huge uproar, and with good reason. Comey was the man leading an investigation into the Trump campaign's potential ties with Russia, and Trump removed him. The reason that Trump originally gave for Comey's firing was his handling of Hillary Clinton's email investigation, which was flimsy to begin with and which he himself has now directly contradicted. If Trump indeed fired Comey because he believed that the FBI investigation was getting too close to the truth on the Trump-Russia scandal, then it would be hard to argue that the move was defensible. There are still big questions as to whether this could count as full obstruction of justice, which would be an impeachable offense. It was, of course, the sort of obstruction of justice that opened Nixon's impeachment proceedings, instead of any of the other crimes that he committed as president.

2 Treason The Hummingbird on Twitter If any of the multiple investigations into the Trump campaign's dealings with the Russians lead to the finding that he did, in fact, actively collude with Russia in order to win the 2016 election, then Republicans in Congress would have little choice but to call it treason and impeach him on that count. So far, though, there is only circumstantial evidence of collusion, and Trump himself has repeatedly and vehemently denied all of the allegations.

3 Violating The Emoluments Clause Astrid Riecken/Getty Images News/Getty Images Everyone learned what the Emoluments Clause of the Constitution was even before Trump's inauguration, just because so many people were saying that his decision not to disassociate himself from his business would put him in violation of it. The clause says that U.S. officials can't accept money from foreign governments, and some have argued that Trump is doing that every time a foreign dignitary chooses to stay at a Trump property. These arguments aren't just coming from the media, though — there's actually at least one lawsuit on the matter. If Trump is found to be in violation of the Constitution in a court of law, then that could be a legitimate reason for impeachment.

4 Bribery Pool/Getty Images News/Getty Images So far, there's no evidence of Trump having bribed anyone, Russian or otherwise, but it has become crystal clear that he does not want anyone getting ahold of his tax returns. There are any number of things that he could be hiding there, like mob ties, scant charitable donations, or a low net worth, but bribery through business dealings could certainly show up, and it would definitely be an impeachable offense.

5 Abuse Of Power David McNew/Getty Images News/Getty Images One of Nixon's articles of impeachment was abuse of power, relating to the way he had "repeatedly engaged in conduct violating the constitutional rights of citizens" and misused his own power and the agencies that he had some level of control over. If Congress wanted to, it seems like Trump has done several things that could fall under that umbrella, from using federal funds to investigate unfounded allegations of voter fraud to potentially taping his conversations with Comey, as he implied in a Friday morning tweet.

6 Political Expediency Alex Wong/Getty Images News/Getty Images When it comes down to it, it's Speaker of the House Paul Ryan and Senate Majority Leader Mitch McConnell who would have to get the impeachment procedures going — which they could be forced into, if a strong enough reason comes up. However, it's not inconceivable that the congressional Republican leaders could decide that it would actually be more beneficial for the party to have Mike Pence as their 2020 presidential candidate rather than Trump — and then they could use any of the reasons that they're currently ignoring in order to launch an impeachment and try to get Trump removed. This is an extremely unlikely case, but I'd say that in 2017, nothing is out of the realm of possibility. Trump is an absolute loose cannon, whereas Pence is a total known quantity. His conservative credentials are as impeccable as they are extreme. Trump's approval ratings are already at near record lows, and should his support from his base start to slip away, then the GOP might like to find a way to replace him instead of risking a huge Democratic victory.