Washington — Many observers say that for Congressman Jack Kemp the goal line is the presidency.
But lately the former star quarterback seems to be following an intricate game plan in pursuit of that objective: He's taking on the President while at the same time avowing his undiminished support for Mr. Reagan.
Breakfasters the other morning were somewhat bemused as the personable Mr. Kemp, always earnest, always enthusiastic, threw the spotlight on the precarious path he must follow.
Kemp is opposing the Reagan-backed tax-increase package. He pushed, perhaps even wrote, the President's tax cut of last year. It was central to Kemp's supply-side philosophy. And he still is convinced, he says, that this relief for the taxpayer, will, with a little more time, bring the economy around.
Kemp calls the tax-increase plan ''a temporary aberration'' on the part of the President and Republicans who are promoting it. But he concedes that it is sending out a confusing, ambiguous signal to the public. ''I agree,'' he says, ''that the President looks like he's trying to lower and raise taxes at the same time.''
''To pass the tax increase now,'' Kemp says, ''is to apologize for what we did last year in cutting taxes. . . . It is no time to be raising taxes on anybody.''
At one point, Kemp hazarded the guess that the tax increases would offset ''about 83 to 85 percent of the tax cut passed last year.''
''How then,'' a reporter asked at one point, could he call the tax-rise plan no more than ''a temporary aberration?'' Here Kemp answered: ''I think the President will see the consequences of this (and do what is best for America.)''
Political observers say that Kemp's only opportunity to gain the presidential nomination in 1984 is if Reagan steps aside and if, and this is a big if, Kemp is perceived by the public as being a Reagan friend and running roughly on a parallel course with the President.
Until recently Kemp has been one of the President's biggest rooters. He started in early as a part of the political advisory group behind the campaigning Reagan. Then he played an important role in helping to shape the President's economic program - perhaps doing more than any one else to persuade Reagan to adopt supply-side economics.
And since then Kemp has been one of the President's team of Republican leaders who have been giving their all, day after day, to get Reagan programs through Congress.
Until now, Kemp himself admits that he has been slipping a bit as a Reagan leader in Congress. But he says he's talking to the President about his position and that Reagan seems to be understanding of what he is doing.
What, then, is Kemp really about these days?
He is, indeed, an ambitious, youthful man who makes no point of trying to hide his aspirations. So, obviously, the presidency is not beyond his hopes.
Also, it seems clear that he is convinced that the President is on the wrong track. And it also seems clear that he has determined to take some political risks - which include the possibility of being thrown off the Reagan team - in order to back up his convictions.
Kemp also isn't happy with the President's move to push through an amendment for balancing the budget. He concedes that it is a sideshow: ''It is diversionary, taking the attention off our main problems,'' he asserts.
But, again and again and in various ways, Kemp keeps emphasizing his loyalty to the President - and that, for the most part, he is in sympathy with Reagan's presidency.
Kemp says he believes he is helping Reagan, too - and this message he also is conveying to the President - in opposing the tax-increase package.
He says that he and his colleagues involved in this battle are intent on ''holding up the tax increase until Congress has met its agreed-to obligations.''
That is, he says that by waging this fight he is helping the President get the tax cuts embraced in the budget.