As the Nixon episode proved, abuse of power is a basis for removal from office.

The latest Trump impeachment trial updates
Not one of the three articles adopted by the Judiciary Committee mentioned a criminal statute, charged Nixon with violating any criminal statute or described how his conduct met the standards set forth in any criminal statute.
It is not surprising that Dershowitz is trying to sweep the Nixon precedent under the rug. It completely demolishes his argument that a president may be impeached only for a criminal act. But it is wrong for Dershowitz to disregard that precedent and pretend it doesnt exist, particularly because almost everyone agrees that the work of the Judiciary Committee against Nixon was a kind of gold standard including Kenneth W. Starr, Dershowitzs co-counsel in the Trump impeachment proceedings.
Even today, the Nixon precedent remains valid and powerful.
The first article of impeachment our committee adopted against Nixon charged him with a variety of acts to delay, impede and obstruct the investigation into the 1972 break-in at Democratic National Committee headquarters at the Watergate hotel. This article did not reference the obstruction-of-justice statute or claim that Nixons actions violated that or any other statute. Indeed, the Judiciary Committees report to the full House explicitly concludes that the impeachment power does not require proof of a criminal act by the president, saying it would be anomalous for the framers … to restrict the grounds for impeachment to conduct that was criminal.
The second and third articles of impeachment were even more relevant. The second was actually dubbed the abuse of power article by committee members at the time. It won the most votes from Republicans on the committee. It, too, did not reference any criminal statute. Instead, it framed Nixons acts in covering up the break-in as an abuse of power. This article essentially charged Nixon with misusing the powers of his office to hide from law enforcement and Congress the involvement of his campaign and top aides in the Watergate break-in in an effort to win reelection a matter that was not intended for the benefit of the American people but for Nixons personal gain.
In fact, the coverup worked and Nixon was reelected in one of the largest landslides in U.S. history.
The second article against Nixon had other, non-Watergate components involving abuse of his presidential power. For example, one of the charges in that article involved Nixons ordering harassing Internal Revenue Service audits of supporters of his presidential challenger, Sen. George McGovern (D-S.D.), as well as other political opponents. Another involved Nixons authorizing the dangling of presidential pardons before the Watergate burglars to keep them from talking to the prosecutors. The committee did not consider these acts to be crimes but they were impeachable offenses.
The third article of impeachment against Nixon related to his refusal to comply with Judiciary Committee subpoenas. Again, no crime was charged. (It is worth noting that the committee did not go to court to seek judicial enforcement of its subpoenas.)
The House Judiciary Committees actions during Watergate reflect the considered position that not all impeachable offenses are crimes and not all crimes are impeachable offenses. Personally, I concluded from the Nixon impeachment precedent that, to constitute an impeachable offense, the presidents misuse of the powers of his office must be grave and substantial, and must threaten our democracy. The articles of impeachment against Trump meet these standards.
As the committee said in its 1974 report: Criminal standards and criminal courts were established to control individual conduct. Impeachment was evolved to cope with both the inadequacy of criminal standards and the impotence of courts to deal with the conduct of great public figures.
The Senate should not fall into the trap of Dershowitzs fallacious arguments.
Read more:
Jennifer Rubin: Adam Schiffs definitive answer for impeachment
George F. Will: There is more utility than futility in the impeachment trial
Greg Sargent: Hannitys ugly meltdown at Romney: Wanting the truth is Trump hatred
Rahm Emanuel: How impeachment could flip the Senate
The Posts View:Republicans are trying to pass off Trumps quid pro quo as a routine presidential act. Thats dangerous.