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It’s a violation of campaign finance law to solicit campaign help from a foreign country, as Mr. Trump knows well from the Russia collusion investigation. It’s also Nixonian.

Although we didn’t know this at the time of his impeachment, Mr. Nixon also secretly sought the help of a foreign government during his 1968 election campaign. Worried that the Vietnam peace treaty President Lyndon B. Johnson was pursuing would cause his defeat, Mr. Nixon sabotaged it by secretly promising South Vietnam it would do better under a Nixon presidency. It worked. The treaty talks failed, voters elected Mr. Nixon, and peace did not come for many more years.

As the legal commentator Benjamin Wittes noted last week on the website Lawfare, in addition to constituting abuse of power, pressuring Ukraine to investigate Mr. Biden and his son for political purposes violates their civil liberties. That also recalls Watergate, because Mr. Nixon violated the civil liberties of Daniel Ellsberg, who was being prosecuted for leaking the Pentagon Papers. Among the grounds for Nixon’s impeachment was his involvement in breaking into Mr. Ellsberg’s psychiatrist’s office, seeking information to smear him.

Like Mr. Nixon’s, Mr. Trump’s reported actions demand impeachment — the one remedy to protect the rule of law, the rights of Americans and the integrity of our elections from a president bent on violating them. The framers created the impeachment power to safeguard democracy. It is Congress’s urgent responsibility to use it now.