For the individuals nominated by the president to sit on the upper levels of the federal bench, there are no qualifications specified other than that the individuals in question should of good standing in their communities. Article 3, section 1 of the Constitution of the United States establishes the Judicial Branch of government, but it states only the following with regard to qualifications or character:
The judicial Power of the United States, shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish. The Judges, both of the supreme and inferior Courts, shall hold their Offices during good Behaviour, and shall at stated Times, receive for their Services, a Compensation, which shall not be diminished during their Continuance in Office.
In other words, individuals nominated by the president to fill openings on the Supreme Court, federal courts of appeal, and district courts need only be of good character. Nothing else is specified. At the lower levels of the federal judiciary, levels established by Congress, such as federal magistrates, there are specified qualifications, such as a minimum number of years as a member in good standing of the individual's state bar. At those higher levels, however, important considerations for filling seats in federal courts are left to the United States Senate, which is vested by the Constitution with responsibility for vetting and confirming candidates nominated by the president.
Because the Constitution does not specify qualifications for federal judgeships, it is, consequently, imperative that the Senate, initially under the guidance of the Committee on the Judiciary, thoroughly vet each nominee. The Committee takes that responsibility very seriously, but one could argue that politics has intruded into the process to such an extent that qualifications possessed by individual nominees are sublimated to broader ideological or political considerations.
Ideally, nominees to fill openings in federal courts can point to long records of admirable work as practicing attorneys and/or as county or state judges new to the federal process. It is hard to argue against practical experience as an important consideration for higher levels of responsibility.
That experience, however, leaves a trail for subsequent examination by those seeking to determine an individual's suitability for the federal courts. How successful has an attorney been at representing the interests of their clients, be that client the government itself (in the case of prosecutors and solicitors) or individuals or organizations involved in criminal or civil litigation? Has the nominee for a federal judgeship ever been sued by a client for malpractice? Has the nominee been reprimanded by his or her state bar for failing to abide the ethical code to which attorneys are bound? These are the most basic considerations for prospective judges.
Beyond the basic questions of competency and ethics is the far more difficult realm of judicial philosophy. What is a nominee's view of various sections of the Constitution? Does the nominee have strong feelings about the Second Amendment to the Constitution, which bestows upon the citizenry the right to own firearms? Supporters of stronger gun-control measures may look askew at nominees with a history of actions or opinions sympathetic to gun-rights activists.
Similarly, what is a nominee's view on the proper role of the federal government in regulating healthcare, especially the infamous issue of reproductive rights? Members of the Senate occupying one side of the ideological aisle will view nominees to the federal courts differently than will those who occupy the other side of the debate. Judicial philosophy is considered the most important benchmark by many senators reviewing nominations to the federal bench. A nominee's view on the proper role of the federal government in regulating society is a key consideration.
One additional consideration when vetting nominees to the federal bench is potential conflicts of interest. Has a lawyer nominated to a federal district court represented clients, such as special interest groups or corporations, that might have issues pending before the court? A lawyer who represents Planned Parenthood, for instance, will be carefully scrutinized by anti-abortion senators and activists when that lawyer is nominated to be a judge. A lawyer is an inherently partisan part of a case; a judge must be neutral in deciding the outcome of that case. Can a previously partisan lawyer become a neutral judge?
These are some of the issues that are routinely considered when individuals are nominated to sit on federal benches. The environment in which nominees are vetted and voted upon has become highly partisan and potentially threatening to the integrity of the process, but that is where it stands.