Defenders of President Donald Trump have repeatedly claimed that the president can't be impeached because he didn't break any laws, despite the fact that Congress does not need to prove explicitly illegal activity to formally impeach a president.
All the same, one official who served in the George W. Bush administration believes that the president very possibly did break federal laws against bribery with his attempt to shake down Ukraine to investigate his political rivals.
Philip Zelikow, a history professor at the University of Virginia, has written an article on Lawfare outlining exactly why the president is in both political and legal jeopardy.
Specifically, Zelikow cites 18 U.S.C. § 201(b), which states that any public official who "corruptly demands, seeks, receives, accepts, or agrees to receive or accept anything of value personally or for any other person or entity, in return for... being influenced in the performance of any official act" is breaking the law.
Zelikow goes on to break down all the ways that Trump's actions in the Ukraine affair seem to fit the bill for breaking this law. Among other things, he shows how Ukraine publicly announcing that it was investigating former Vice President Joe Biden undoubtedly counts as a thing of value to the president.
"There is no doubt that these demands were things of great value to Trump," he writes. "Federal bribery law does not require that the value be in money. As the Department of Justice Criminal Resource Manual points out, such things include 'intangible as well as tangible things' and 'have been broadly construed to focus on the worth attached to the bribe by the defendant, rather than its commercial value.'"