The US House of Representatives will vote this week on whether to impeach President Donald Trump on charges that he abused the power of his office and obstructed Congress in its investigation of his dealings with Ukraine.
The following defines the two charges, or "articles of impeachment," based on historical background.
Abuse Of Power:
In the impeachment context, abuse of power is generally defined as using the vast powers of the presidency for personal benefit.
Abuse of power is not specifically referred to as an impeachable offense in the US Constitution, which states that a president can be removed from office for "Treason, Bribery, or other high Crimes and Misdemeanors."
But the founders of the United States intended the phrase "other high Crimes and Misdemeanors" to broadly encompass abuses of power, legal scholars said.
Alexander Hamilton, a famed American statesman, wrote in1788 that impeachment proceedings were for "those offenses which proceed from the misconduct of public men, or, in other words, from the abuse or violation of some public trust."
Louis Michael Seidman, a professor at Georgetown Law, said the core allegation against Trump - that he withheld security aid to Ukraine to pressure it to announce investigations that would benefit him politically - was the sort of conduct the founders considered impeachable.
"The US has a national security interest in Ukraine and it does appear that what the president was doing was putting that national security interest at risk in exchange for political benefits," said Seidman. "If that is what happened, that is the core of what impeachment is about."
Abuse of power was one of the articles of impeachment advanced against President Richard Nixon, who resigned before a full House vote on the charges. In approving the charge of abuse of power against Nixon, a House committee accused of him of authorizing tax audits of political opponents on his "enemies list."
Abuse of power was advanced as an article of impeachment against former President Bill Clinton relating to his affair with a White House intern, but a majority of House members voted against including that charge. Clinton was eventually impeached on two other charges - perjury and obstruction of justice - but was not convicted by the Senate.
Obstruction Of Congress
Democrats have also charged Trump with obstruction of Congress based on his stonewalling of the House's impeachment inquiry. The White House has refused to provide documents to congressional investigators and has instructed top advisers and government officials to defy subpoenas and refuse to testify.
A similar charge, contempt of Congress, was one of the articles of impeachment against Nixon, who had defied subpoenas for incriminating tape recordings.
Contempt of Congress is a misdemeanor crime under US law, which defines the offense as willfully failing to provide testimony or documents to Congress. A different crime, obstruction of justice, more broadly prohibits "interference with the orderly administration of law and justice."
The White House has argued that the Constitution does not require senior presidential advisers to appear for compelled testimony before Congress. A judge rejected that argument onNov. 25 in a dispute over a subpoena issued to former White House counsel Don McGahn.
Trump's lawyers have also argued his refusal to cooperate with the impeachment investigation is justified because the process has been unfair to him.