Fred Wertheimer is the founder and president of Democracy 21 , a nonprofit, nonpartisan organization that seeks to promote government accountability and integrity. The opinions expressed in this commentary are those of the author. View more opinion articles on CNN.

Of course, this ludicrous comparison leaves out that no one in modern US political history recalls Sen. McCarthy more than President Trump. But beyond that, it's not Trump or Mueller whose situation evokes a McCarthy comparison at the moment -- it's House Speaker Paul Ryan.

Why? Recall that in 1954, Sen. McCarthy faced and failed a famous " sense of decency " moment. In a nationally televised Senate hearing, McCarthy attacked Fred Fisher, a young lawyer in the law firm representing the US Army, McCarthy's latest target in his years-long demagogic and unsuccessful hunt for communists in the government. Fisher had been briefly associated in law school with the National Lawyers Guild, an organization thought to be associated with the Communist party.

Joseph Welch, the law firm's counsel attacked McCarthy's cruelty and recklessness. He then delivered the coup de grace, saying "Have you no sense of decency, sir, at long last? Have you left no sense of decency?" Fisher went on to become the president of the Massachusetts Bar Association and McCarthy's reputation was destroyed and his career ultimately ended.

Which brings us to House Speaker Ryan.

In January, Speaker Ryan's 20-year career in Congress will come to an end.

Next month, Republican Representatives Mark Meadows from North Carolina and Jim Jordan from Ohio -- both leaders of the Freedom Caucus -- are expected to press Speaker Ryan to bring to the House floor their resolution to hold Deputy Attorney General Rod Rosenstein in contempt of Congress for his failure to turn over documents tied to the Russia investigation. Back in May, despite threats of impeachment, Rosenstein was adamant that the Justice Department was "not going to be extorted."

And here is where Speaker Ryan will get his "decency" test:

Does he stand up for Rosenstein, a highly regarded public official with a long, successful and respected career in law enforcement? Or does Ryan schedule a House floor vote on a meritless and politically motivated resolution to hold Rosenstein in contempt of Congress?

Rosenstein, who oversees the Russia investigation, has been under relentless attack for months by President Trump and his House loyalists . The goal of these attacks is clear -- to discredit, cripple and, if possible, kill the Russia investigation.

As part of this effort, Meadows and Jordan were among GOP leaders that recklessly filed articles of impeachment against Rosenstein just before the House left for its August recess. The alleged "grounds" for impeachment were Rosenstein's failure to comply with a Republican House Committee subpoena requesting the Russia probe documents.

The Justice Department has a longstanding policy of not releasing these kinds of investigative documents in the middle of a criminal investigation. Doing so could compromise the investigation if the information reaches the individuals under investigation -- a particular danger here, as President Trump and Rep. Meadows reportedly are key allies.

Nevertheless, in an effort to be as accommodating as possible, Rosenstein and the Justice Department have been providing the House with numerous documents from the Russia investigation.

To his credit, Speaker Ryan opposed the impeachment effort and noted that the House had made "tremendous progress" in getting the Justice Department to provide the documents it wanted. So far, so good.

Meadows and Jordan ultimately dropped their impeachment gambit and instead asserted that they would pursue a contempt of Congress resolution against Rosenstein in early September if all of the documents Republicans have subpoenaed are not received by the start of the month. According to a published report , Meadows claimed Ryan had agreed to this approach: "The speaker is willing to support [Judiciary] Chairman [Bob] Goodlatte in a contempt process if the agreed upon documents are not delivered."

The impeachment resolution was nothing more than an empty threat. In the 229-year history of the Constitution, Congress has never impeached a subcabinet official, such as a deputy attorney general. When Meadows and Jordan tried this reckless act in 2016 against IRS Commissioner John Koskinen, their baseless impeachment resolution offered was overwhelmingly defeated by a bipartisan vote of 342 to 72

However, if a contempt of Congress resolution against Rosenstein for failing to comply with Republicans' subpoena is brought to the floor, it might just pass on a party-line vote.

If that were to happen, the contempt resolution would serve the same purpose as articles of impeachment. It would give President Trump "cover" to remove Rosenstein from his job and to replace him with a Trump loyalist and take control of (and kill) the Russia investigation. This is what the Meadows and Jordan effort against Rosenstein is really about.

Ryan will face his "sense of decency" moment in September.

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He can end his career in Congress on a high note, preserve his integrity and show his "sense of decency" by blocking the effort by Meadows and Jordan to slander and stain Rosenstein's reputation and record of public service.

Or, he can leave an indelible black mark on his reputation by enabling a contempt of Congress resolution against Rosenstein to be voted on and passed -- and demonstrate that, like Senator McCarthy, Ryan has "no sense of decency."

Correction: An earlier version of this article incorrectly stated the name of the counsel for the US Army in 1954. It was Joseph Welch, not Robert Welch.