JACK KEMP, in running for the presidency, makes a fair claim to be the ideological and political heir to Ronald Reagan. Like Reagan through much of his career, however, Kemp is not the ready heir of the Republican Party apparatus. The New York congressman's background in sports, his first political scrimages in Reagan-run California, his credibility among working class Americans, his consistency on doctrines like holding the line on taxes and pushing ahead on Star Wars - from Kemp's populist style to his motivation by ideas, he is cut from a Reaganesque mold. It was Kemp who popularized the notion of the stimulative effect of tax cuts, central to Reaganomics. He relishes the give and take of debate - though his ripostes tend to come in long paragraphs, not Reagan one-liners.
But it is Vice President George Bush, Reagan's strongest rival in 1980, who is sopping up the early party faithful allegiance. Bush is positioned a lot like Vice President Walter Mondale, the Carter administration's natural heir in 1984. Bush leads in the polls, followed by Sen. Robert Dole, the congressional establishment leader. It is of little consequence now that Reagan personally might have favored Kemp as running mate in 1980: The Reagan team opted to balance the ticket by absorbing the moderate opposition, represented by Bush. Bush and Dole have earned their own claims to political inheritance by loyally supporting Reagan policies even when they might have preferred a more pragmatic,moderate or compromising course.
Kemp and others should note, however, that 1988 begins the post-Reagan political era. Over a full eight years, Reagan's policies will have had their shot. The political appetite is shifting from the ``Reagan revolution'' against government (despite record federal spending) to a re-evaluation of government's constructive role. The next nomination will not be Mr. Reagan's to bestow.