WASHINGTON — One day in October 1992, four Republican congressmen showed up in the Oval Office with an audacious recommendation. President George Bush was losing his re-election race, and they told him the only way to win was to hammer his challenger Bill Clinton’s patriotism for protesting the Vietnam War while in London and visiting Moscow as a young man.

Mr. Bush was largely on board with that approach. But what came next crossed the line, as far as he and his team were concerned. “They wanted us to contact the Russians or the British to seek information on Bill Clinton’s trip to Moscow,” James A. Baker III, Mr. Bush’s White House chief of staff, wrote in a memo later that day. “I said we absolutely could not do that.”

President Trump insists he and his attorney general did nothing wrong by seeking damaging information about his domestic opponents from Ukraine, Australia, Italy and Britain or by publicly calling on China to investigate his most prominent Democratic challenger. But for every other White House in the modern era, Republican and Democratic, the idea of enlisting help from foreign powers for political advantage was seen as unwise and politically dangerous, if not unprincipled.

A survey of 10 former White House chiefs of staff under Presidents Ronald Reagan, Bush, Clinton, George W. Bush and Barack Obama found that none recalled any circumstance under which the White House had solicited or accepted political help from other countries, and all said they would have considered the very idea out of bounds.