WASHINGTON — In the summer of 1974, a young law student named Zoe Lofgren, working for a member of the House Judiciary Committee, drafted what she thought was an ill-advised article of impeachment charging President Richard M. Nixon with usurping the power of Congress by concealing the bombing of Cambodia.

The committee rejected it. “It didn’t pass and it shouldn’t have passed,” Ms. Lofgren said.

Now Ms. Lofgren is Representative Zoe Lofgren, Democrat of California, a close ally of Speaker Nancy Pelosi, a senior lawmaker on the judiciary panel and the panel’s only member to have participated in all three modern presidential impeachments. And much like 45 years ago, she has emerged as a voice of restraint as her party barrels toward a divisive and partisan impeachment of President Trump.

On Wednesday evening, the Judiciary Committee opened its formal debate on two articles of impeachment — abuse of power and obstruction of justice — stemming from the president’s campaign to enlist Ukraine to investigate his political rivals. To Ms. Lofgren, who has presented herself as the party’s institutional memory on impeachment, the articles were a triumph of facts over emotion.

“I think they are well crafted,” she said in an interview, in her careful, measured way, “and, unfortunately, supported by the evidence.”