Minnesota’s First District Rep. Jim Hagedorn borrowed a phrase from former Supreme Court Justice Potter Stewart when he said at his Madelia town hall meeting Wednesday his definition of an impeachable offense is, “you know it when you see it.”

Stewart said of pornography in a Supreme Court case, “I know it when I see it.”

An impeachable offense, then, like pornography, may be hard to define, but a workable definition is needed. Some people have seen a whole litany of impeachable offenses in President Donald Trump’s first two years, while others, like Hagedorn, have seen nothing.

There is not a lot of precedent to go on. In the 230 years since George Washington was first sworn in as president, only twice has the House voted to impeach a sitting president. Andrew Johnson was impeached in 1868 for violating the Tenure of Office Act by removing the Secretary of War against Congress’s wishes. The impeachment failed in the Senate by one vote.

President Bill Clinton was impeached in 1998 for lying under oath and obstruction of justice when he denied having an affair with his intern, Monica Lewinski. Again, the Senate did not convict him and he remained in office.

President Richard Nixon was headed for impeachment in the House and would have undoubtedly lost in the Senate, so he resigned before that could happen. His participation in the coverup of the Watergate affair certainly fit Hagedorn’s definition. Everyone saw it, and knew it.

Impeachment of a president is a serious matter, one that should not be undertaken to settl political differences, as Johnson’s and Clinton’s seem to have been. There are certainly political overtones in the current impeachment inquiry being conducted by the Democrats in Congress. But there are serious allegations against the president that should be looked into.

The final blow to Nixon’s presidency was the revelation of the White House tapes, and the suspicious 18-1/2 minute gap in those tapes during which he allegedly discussed the Watergate coverup with his aides. It may take evidence as unimpeachable as that to convice Republicans to go along with impeachment. As for now, they don’t see it.