10 Things You Need To Know About Blue Slips: Republicans repeatedly used the tradition to block President Obama’s judicial nominees. (Huffington Post, 09/13/17) Christopher Kang, Former Deputy Counsel to President Obama

Letter from 53 Law Professors Urging Hearing & Prompt Vote on Victoria Nourse v. Sen. Ron-Johnson "One-Person-Filibuster" (07/14/11)
"We urge you to hold a Senate Judiciary Committee hearing and seek a prompt vote for Seventh Circuit nominee Victoria F. Nourse.... Purely as a matter of process, this delay raises serious questions about whether the Senate is fulfilling its constitutional role to provide the President’s nominees with a prompt hearing and full Senate vote. ... A nominee of sterling credentials, who has served her country under Republicans and Democrats, who was approved by a state merit commission, and praised by the A.B.A., should not be subject to unending delay. For a single Senator from one state within the Circuit to assert a hold, months after the nomination was complete, undermines Wisconsin’s meritbased selection system, blocking highly qualified nominees from a hearing and a vote....A hold without reason is an arbitrary Senatorial process, for any nominee of any party. It allows one Senator the ability to bar a hearing and a vote on a nominee with broad based support. The effect is an unbreakable one-person-filibuster."

As the Constitutional Accountability Center explained:

In 2009 – when the judge who previously held this Seventh Circuit seat announced his intention to take a form of semi-retirement available to federal judges known as “senior status” – Wisconsin’s then-Senators Russ Feingold and Herb Kohl activated the Wisconsin Federal Nominating Commission to recommend the names of candidates to fill the impending vacancy. Of the six names recommended by the Commission at that time, Senators Feingold and Kohl forwarded four to President Obama for his consideration.

From that list the President nominated Victoria Nourse in 2010. The Senate’s consideration of the Nourse nomination languished into 2011, however, after Senators Feingold and Kohl had been replaced by current Senators Baldwin and Ron Johnson. Once he took office, Senator Johnson decided to oppose the Nourse nomination, blocking her from even receiving a hearing in the Senate Judiciary Committee. Nourse finally withdrew her name from further consideration in 2012, saying “the system is broken.”

A Judging the Environment Letter to the Editor provided context:

Glenn Sugameli: Ron Johnson still blocking OK for judges (Capital Times (WI), 12/30/11)
Letter: "Wisconsin’s Ron Johnson is the “only freshman GOP senator blocking own state’s judicial nominees.” Indeed, with the support of other freshmen Republican senators from five states, the Senate has confirmed all 10 of the other nominees for judgeships that President Obama re-submitted after the senators were elected. In contrast, despite nonpartisan and bipartisan criticism, Johnson blocked Senate hearings for Victoria Nourse (7th Circuit Court of Appeals) and Louis Butler (Western District of Wisconsin), and forced the nominations to be returned to the president.”