It is understandable that liberal Democratic presidents, beginning with Franklin D. Roosevelt, loaded the Supreme Court with liberal, Democratic justices.
What is far harder to understand is how a whole succession of conservative Republican presidents -- Nixon, Ford, Reagan, and Bush 41 -- managed to appoint so many liberals to the Supreme Court.
All these presidents ran on the idea that what courts in general, and the Supreme Court in particular, needed were judges who followed the law instead of making up their own new laws.
Voters who put these Republican presidents in the White House repeatedly found themselves disappointed with many, if not most, of their nominations of Supreme Court justices.
President Nixon appointed Harry Blackmun, who created a "constitutional right" to an abortion out of thin air, just as previous liberal justices had created all sorts of constitutional rights out of thin air for criminals, vagrants, and others.
President Ford appointed John Paul Stevens, whose long history of liberal votes was climaxed by his 2005 decision that politicians can seize private homes and turn them over to other private individuals, who want to replace these homes with amusement parks or shopping malls -- which bring in more tax revenues.
Even Ronald Reagan, so eloquent against group preferences and quotas, announced that he was going to appoint "a woman" to the Supreme Court during the 1980 election campaign -- and later looked for a woman to appoint.
That is how a mid-level state court judge with no experience in the federal judiciary became Justice Sandra Day O'Connor. Yet no one said that she was "unqualified" as they would later say of Clarence Thomas, whose credentials greatly outweighed hers.
Now, a quarter of a century later, Sandra Day O'Connor's legacy of incoherent Supreme Court opinions on such issues as affirmative action and abortion have made a mockery of the very concept of law.
Given the momentous impact of Supreme Court decisions on 300 million Americans today and on generations yet unborn, it is staggering that either presidents or justices themselves cannot keep their eye on the ball and understand the high stakes at issue.
Sandra Day O'Connor was quota-minded from before she was appointed and after she retired. Even before she herself was in the running, she had urged President Nixon to appoint "a woman" to the Supreme Court and, decades later, she lamented that President Bush did not appoint "a woman" to succeed her.
The stakes for the country and the pressures on Supreme Court justices demand that the best people possible be put on the High Court. If that turns out to be nine Asian American men or nine Hispanic women, that is just a footnote to history.
But to start out looking for "diversity," as if you were decorating a Christmas tree with different colored baubles, is to abdicate one of the most solemn responsibilities of a president.
The endlessly repeated mantra of "diversity" is a triumph of the art of propaganda, for not a speck of hard evidence to support it has been asked for or given. Yet President George W. Bush cited "diversity" when he decided to make the aborted nomination of Harriet Miers to the Supreme Court.
Whatever the shortcomings of Democrats, they know what they are for -- and are willing to go all out to fight for it. Republicans often seem ambiguous about what they are for and seem to regard fighting as ungentlemanly.
Senate Democrats went all out to stop the nomination of Judge Robert Bork to the Supreme Court and to try to stop the nomination of Judge Clarence Thomas. These Democrats did not let either truth or decency cramp their style.
But Republicans voted overwhelmingly to confirm liberal-left nominees Ruth Bader Ginsburg and Stephen Breyer when Bill Clinton nominated them. The Senate vote was 87 to 9 for Breyer and 96 to 3 for Ginsburg.
No need to savage either nominee, but they should have been voted against -- and the reasons for those votes explained to the public. Otherwise Democrats define what is a "mainstream" judge.
Republicans need to rethink their views on judges -- or perhaps to really think for the first time.