By any yardstick, a Ronald Reagan presidency would bring distinct changes to the United States, affecting not only Americans but peoples overseas. Despite Sen. Edward M. Kennedy's campaign description of President Carter as a clone of Mr. Reagan, clear differences stamp the policies of the two men.
Some of these, like income tax policy, are obvious. Others, involving foreign affairs, are less so.
Mr. Carter himself, speaking Wednesday in New York, called the differences between him and Reagan "brutal," both in their respective concepts of where America now stands and where the nation should go.
Analysts stress that, so far, they are dealing with Reagan's campaign rhetoric, which might be tempered if he became president -- just as Carter's performance in office differs from his 1976 goals.
In foreign affairs, experts single out the Soviet Union, the Middle East, and Taiwan as key areas in which Reagan's policies, as so far expressed, split with those of President Carter.
With his talk of achieving military superiority over the Soviets, Reagan alarms many West Europeans, who fear being caught in the middle of a superpower arms race.
US defensive strength, said Reagan in his nomination acceptance speech, is at "its lowest ebb in generation, while the Soviet Union is vastly outspending us in both strategic and conventional arms."
He opposes the SALT II treaty to limit nuclear weapons, claiming it is advantageous to the Soviets. he would, he says, negotiate a treaty to "genuinely limit strategic nuclear weapons."
America's European allies, together with State Department experts, see no chance that Soviet leaders would scrap SALT II in favor of a treaty acceptable to Reagan.
End result of Reagan's Soviet stance, said a US expert, might be "deep strains within NATO, with many Europeans basically disagreeing with US policies."
Even now, despite the Soviet invasion of Afghanistan, several West European governments are reluctant to impose -- at President Carter's urging -- the kind of economic sanctions against Moscow that might jeopardize future trade.
As for the Middle East, Reagan's ringing support of Israel, including the latter's sovereignty over an undivided Jerusalem, would make it harder for moderate Arab leaders to cooperate with the US, analysts believe.
Reagan describes Israel as a staunch US ally, whose armed forces act as a deterrent to Soviet expansion in the Middle East. This primacy of Israel, in Reagan's rhetoric, so far is not matched by equal consideration of the strategic role played by Saudi Arabia, largest oil supplier to the United States.
Some analysts note what they call an inconsistency in Reagan's position. At home, he wants all price controls removed from domestic oil, reduction of the windfall profits tax on US oil companies, and the "return" of energy development to energy firms.
This accords with the views of giant US oil companies, whose officials, on the other hand, long have pleaded for a more evenhanded Arab-Israel approach from the US government.
Deploring what he calls the Carter abandonment of Taiwan, a "longtime ally and friend," Reagan advocates restoration of some kind of official US-Taiwanese relations, though not necessarily full diplomatic ties.
President Carter broke relations with the Taipei government when the United States exchanged ambassadors with the (mainland) Peoples Republic of China.
Chinese communist leaders, alert to Reagan's views, rumble warningly against resumption of government-to-government relations between Washington and taipei.
Apparent to most Americans is the striking difference between Reagan's advocacy of a 10 percent, across-the-board income tax cut, effective next Jan. 1 , and Carter's rousing attack on that proposal as inflationary.
In fact, analysts note, tax policy ultimately is decided by Congress, so that Reagan's jurisdiction, even as president, would be limited.
This stands in contrast, some analysts note, with foreign policy, which primarily is the responsibility of the president, not Congress.
Reagan and Carter share a desire for a balanced budget. But the Republican challenger would sharply boost military outlays and correspondingly trim social spending to reach that goal.
Mr. Carter and his advisers say that cannot be done without cutting into the bone of programs that support poor, elderly, and also disadvantaged Americans.
Zealous as Carter is to reduce government regulation of the economy, REagan likely would go him one better -- all with the aim of unshackling industry to achieve higher output and productivity.