Appellate judges appointed by Presidents Ronald Reagan, George H.W. Bush and George W. Bush show more conservative voting patterns than do judges appointed by any president in the past 80 years. As a result, the average vote of a federal judge has been growing much more conservative.

The conservatism of Republican appointees in recent decades can be found in many contentious areas of the law. It is particularly pronounced in these:

* On the federal courts of appeals, Reagan, Bush I and Bush II appointees have been sharply opposed to campaign finance regulation, voting to uphold it just one-fourth of the time. Carter and Clinton appointees, in contrast, have voted in favor of campaign finance regulation at twice that rate.

* Reagan, Bush I and Bush II appointees have voted in favor of those complaining of disability and sex discrimination less than one-third of the time, while Carter and Clinton appointees have done so about half the time.

* Appointees of Carter and Clinton voted to uphold affirmative action programs about three-quarters of the time. Reagan, Bush I and Bush II appointees have done so only half as often.

* Here's the biggest difference of all: Recent Republican appointees have voted for gay rights only 11 percent of the time, Carter and Clinton appointees 70 percent.

These are the areas in which Kerry nominees would be likely to differ from Bush appointees. Substantial differences can also be found, and should continue to be expected, in at least four others: environmental protection, abortion, capital punishment and employment discrimination against African Americans.

In these areas, the choice of the next president could dramatically affect the content of federal law.

(The differences do not extend to all areas. Contrary to expectations, for example, Republican appointees do not differ from their Democratic counterparts in criminal cases. Both are highly likely to reject criminal appeals.)

Presidents Reagan, Bush I and Bush II have appointed judges far more conservative than those of fellow Republican Richard M. Nixon, though Nixon also emphasized the importance of changing the liberal face of the federal judiciary. In a large set of cases, Nixon appointees issued liberal votes 54 percent of the time, about the same rate as Clinton appointees, while Reagan and Bush appointees have issued liberal votes only 41 percent of the time.

Remarkably, there are no significant differences among the voting records of Reagan, Bush I and Bush II appointees. The three most recent Republican presidents have shown extraordinary consistency in their choices.

This is not to say that the generally conservative trend has been limited to Republican presidents. Judges appointed by President Bill Clinton have been more conservative than those appointed by John Kennedy, Lyndon Johnson and Jimmy Carter. Indeed, Clinton's choices have similar overall voting records to those of Republican presidents Nixon and Gerald Ford.

Still, of the 15 most conservative judges serving on federal appellate courts in the past two decades, no fewer than 12 were chosen by Reagan and the elder Bush. (There are not yet enough votes to reliably rank individual appointees by George W. Bush.) Of the 15 most liberal judges, 13 were chosen by Jimmy Carter and Bill Clinton.

Several things are clear: Clinton's appointees show more conservative voting patterns than those of Democratic predecessors Carter and Johnson. Reagan's appointees and those of the two Bushes show more conservative patterns than the judges named by GOP predecessors Nixon and Ford. The federal judiciary has been moving steadily to the right.

Cass R. Sunstein is a professor at the University of Chicago Law School. David Schkade is a professor at the Rady School of Management of the University of California at San Diego.