Sooner or later, Donald Trump will leave office. Later, in his case, means just five years from now. But what is likely to be the greatest achievement of his presidency will live on for decades to come.

It is the transformation of a liberal-leaning federal judiciary into one that is infused with conservative views and beliefs. For years and years, like it or not, for better or for worse, it will affect you, your family and your business. This remaking of the courts was not the product of happenstance. Rather, it was accorded high priority and implemented with care, thought and dedication to purpose.

With the exception of a few specialised courts, cases involving federal civil and criminal matters are heard in United States District Courts. They are the hub of federal litigation; 450,000 cases brought in 2018. A sole federal district court judge presides over each proceeding; jury or nonjury. There are 673 authorised district court judges in 94 district courts with at least one court in every state.

A party against whom an adverse decision is rendered by a district court may appeal that decision, as of right, to a United States Court of Appeals. There are 13 circuits in which these courts are located. In 2018, 50,000 appeals were filed.

There are 179 authorised judges for these appellate courts. Cases are heard and decided by three judge panels selected at random.

The Supreme Court is the final step. With rare exceptions, litigants do not have a right to appeal to the Supreme Court. Accepting an appeal is a matter of discretion. It takes four of the nine Justices to consent for a case to be heard.

The grant of appeal is bestowed on very few. Each year several thousand petitions for review are filed — each year the Court hears about 70 to 90.

Because recourse to the Supreme Court is so limited, in practice the courts of appeals are the courts of last resort for almost all litigants. This being the case, the importance of the courts of appeals cannot be overstated. Their impact is significant and their judicial philosophy affects the course of justice in a meaningful and consequential manner.

Judges on all these courts are nominated by the President, subject to confirmation by the Senate. What is important — exceedingly important — is that they are lifetime appointments. No term limits. No renomination required. That provides the possibility for a president to effect a desired long-term repositioning of judicial philosophy if he is able to nominate successfully a sufficient number of judges similarly disposed during his tenure. It is generally accepted, to the pleasure of some and the pain of others, that Trump has effectively accomplished that.

There are 861 authorised judgeships in total for the Supreme Court, the courts of appeals, and the district courts. The number of authorised judges serving at present is 788 — 382 of those judges were appointed by Republican presidents, including Trump; 406 by Democrats. But the president has made 54 additional nominations to these courts that are pending in various stages of the process. If confirmed, which is virtually certain, there will be a majority of active Republican judges — 436 to 406. A significant Democratic majority will have been erased by the end of his first term in office with still more to come.

Quite a feat.

An interesting, and not insignificant footnote, is that there are now 594 semi-retired federal judges referred to as senior active judges. These judges preside over a reduced case schedule. In the aggregate, however, their dockets make up about 15 per cent of the caseload — 365 of those judges were Republican appointees; 226 Democratic.

Trump’s judicial appointments have resulted in a clear conservative shake-up of the federal judiciary. The breadth, depth and longevity of this sea change is recognised and acknowledged by observers of all political stripes, and feared by interest groups that anticipate it will result in adverse consequences to them.

The president has made two appointments to the Supreme Court: Justice Neil Gorsuch and Justice Brett Kavanaugh.

The significance of their ascension to the Court far outstrips their number. For those two seats have cemented a conservative 5-4 majority. Although one cannot and should not expect rigid adherence by all in the new majority to a diet of deep conservatism, the trend will be clear and unmistakable — it will undo and obstruct liberal interpretation and application of the law. Should at least one of the Supreme Court seats now held by one of the four Democrats become vacant during Trump’s term in office the split becomes 6-3. Daunting.

Forty-eight of Trump’s confirmed nominees have been to the courts of appeals. He has made more courts of appeals nominations at this point in his presidency than any other president. The consequences of these initial appointments are impressive. The majority in two of the 13 circuits have flipped from Democratic to Republican. One circuit has become evenly divided. And the Democratic majority in three others is now razor-thin. Democrats and Republicans each have a majority in six of the circuits, with one tied. If the Republicans take majority control in all of the four circuits up for grabs, they would have ten to only three for the Democrats. This scenario is not implausible.

And these conservative Republican jurists are not going anywhere — at least not soon. The average age of all judges appointed by Barack Obama was close to 60. The average age of the judges appointed by Trump is 49.4. It is estimated that on average they will serve for 30 years — a generation or more. Accident?

The House of Representatives plays no role in the selection or confirmation of federal judges. With a Republican-majority Senate throughout Trump’s time in office, the flow of nominations and confirmations has gone steadily on, notwithstanding a standstill in congressional legislation as the Democrat-controlled House of Representatives focuses on impeachment.

Trump’s key ally and architect of the takeover is Mitch McConnell, of Kentucky, the Senate majority leader. It has been McConnell’s goal for quite some time to establish a dominant conservative federal judiciary. It is reported that he told Trump at the onset that his overriding priority should be the transformation of the judiciary into conservative hands.

The Republican-controlled Senate, under McConnell’s leadership, took some bold steps during Obama’s last years in office. It blocked or stalled Senate consideration of Obama’s judicial nominations.

Most notable was McConnell’s refusal to have the Senate take up the nomination of Merrick Garland to the Supreme Court. No hearing. No vote.

Unprecedented to deny a president any consideration at all of a Supreme Court nominee. Notwithstanding withering criticism from Democratic legislators and some in the media, McConnell and his Republican colleagues stood their ground. They were gambling that a Republican would be elected president in 2016.

The odds for that seemed long when it appeared, from the polls and those in the know, that Hillary Clinton would defeat Donald Trump. Clinton’s confidence in the outcome was palpable. She was assured by the poll numbers and envisioned a large popular-vote margin. But she forgot to count the electoral college votes. Donald Trump did not forget. To shock and surprise, he became the 45th president of the United States. The McConnell-led gamble paid off. Big time.

On his first day in the Oval Office, Trump had an astonishing 100 judicial vacancies to fill, including one to the Supreme Court. A pretty good jump start!

We are on the cusp of a judicial changeover that will have consequences for our country and our society for an extended period of time. It will long survive shifting political winds and write a new and singular chapter in the annals of the federal courts.

• Stuart E. Seigel is Senior Consultant to The Dilenschneider Group. He has served as Chief Counsel of the Internal Revenue Service and in several other posts in the Federal Government. He also engaged in the private practice of law in Washington and New York. This opinion was written before the passing of Ruth Bader Ginsburg