The more deliberate the inquiry, the better chance that the American people will have confidence in it. For Nixon, the process that led to his resignation took more than two years, and the scope of wrongdoing that those investigations revealed was breathtaking. The House Judiciary Committee and a Senate select committee undertook meticulous fact-finding, which ultimately uncovered the evidence that Nixon had taped every conversation in the White House.

Three days after the Supreme Court ordered Nixon to turn over dozens of taped conversations, the House Judiciary Committee approved three articles of impeachment, including one charging that Nixon obstructed justice by paying hush money to the Watergate burglars. Twelve days later, Nixon resigned. Ever since, people on both sides of the aisle have had confidence in the justice of that outcome.

Many advocates on both sides are too eager for a quick resolution of the investigation into Trump's campaign — Democrats to remove the president from office and Republicans to exonerate him. Moving too quickly not only risks a sloppy and incomplete investigation but also subjects the outcome to claims of either a whitewash or of overturning the results of an election held just months ago.

The selection of Robert Mueller as special counsel to oversee the investigation of possible collusion between Trump's campaign and Russian agents presents a good model for the House to follow. A former FBI director, Mueller comes to the task with a reputation of impeccable integrity, just as Archibald Cox did when he was appointed as Watergate special prosecutor. If Mueller conducts the investigation as expected, rigorously and impartially, the public will likely have a great deal of confidence in the outcome, whatever it may be.

Impeachment requires proof of significant abuse of power or breach of public trust. Obstruction of justice, or even the attempt to obstruct, epitomizes that sort of offense, entailing as it does an attack on a system whose integrity the president has sworn to uphold.

By contrast, Presidents John Tyler and Andrew Johnson faced constant threats of impeachment largely because they were remarkably unpopular. The House tried but failed three times to impeach Tyler for having done nothing more than protect the president's authorities to veto legislation and nominate officials. Even though Johnson came within a single vote of being convicted in the Senate, most historians have dismissed his impeachment as driven more by partisanship than a proper basis for impeachment and removal.

Impeachment is serious business, perhaps the most serious other than going to war that Congress ever contemplates. Any impeachment inquiry must be conducted thoroughly and preferably with bipartisan support. Those eager to get started must remember: If not done properly the first time, there might not be another chance.