It appears that the Republicans may be using the "secret memo" as an excuse to attack Deputy Attorney General Rod Rosenstein.

Courtesy of the New York Times:  

A secret, highly contentious Republican memo reveals that Deputy Attorney General Rod J. Rosenstein approved an application to extend surveillance of a former Trump campaign associate shortly after taking office last spring, according to three people familiar with it. 

The renewal shows that the Justice Department under President Trump saw reason to believe that the associate, Carter Page, was acting as a Russian agent. But the reference to Mr. Rosenstein’s actions in the memo — a much-disputed document that paints the investigation into Russian election meddling as tainted from the start — indicates that Republicans may be moving to seize on his role as they seek to undermine the inquiry. 

The memo’s primary contention is that F.B.I. and Justice Department officials failed to adequately explain to an intelligence court judge in initially seeking a warrant for surveillance of Mr. Page that they were relying in part on research by an investigator, Christopher Steele, that had been financed by the Democratic National Committee and Hillary Clinton’s presidential campaign. 

Democrats who have read the document say Republicans have cherry-picked facts to create a misleading and dangerous narrative. But in their efforts to discredit the inquiry, Republicans could potentially use Mr. Rosenstein’s decision to approve the renewal to suggest that he failed to properly vet a highly sensitive application for a warrant to spy on Mr. Page, who served as a Trump foreign policy adviser until September 2016.

Of course if the Republicans manage to undermine Rosenstein's reasoning behind his Carter Page warrant, they can then move on to attacking his judgement in appointing Robert Mueller and can start working to further undermine the investigation.

Obviously this is an attempt to accomplish what Trump wanted when he tried and failed to fire Robert Mueller, and do it in a way that the Republicans feel offers some protection from accusations of obstructionism.

But of course it does no such thing, because it is only the most recent in a long line of attempts to obstruct this investigation. 

Which we saw more of today with the firing of Andrew McCabe.