In a year's time Vice-President George Bush has gone far to right wing Republicans in his favor. Should President Reagan decide to step aside three years hence, Mr. Bush thus is becoming an acceptable alternative among these Republican loyalists.
The hardest of the hard-core Republicans are in southern California. These are the Republicans who, above all, were unhappy when Mr. Reagan chose as his running mate his leading opponent during the primaries. They distrusted Bush. They saw in his views the kind of Eastern seaboard moderate that they had long opposed. Never mind that he now hailed from Texas. Bush's roots were in Connecticut and Yale - and those were the ties, as these Republicans saw it, that really counted.
But in a relative few months Bush's cooperation with Reagan has been so apparent and his rhetoric so compatible to conservative ideology that the vice-president has worn down much of this hard-core conservative GOP opposition.
From conversations with rank-and-file conservatives and with members of the right-wing power structure this view of a possible Reagan succession surfaces:
* There is no disposition among these conservatives to see Reagan serve only one term. As Herbert Klein, former press secretary under Nixon, says: ''The Republicans around here feel that Reagan is indispensable to getting their programs enacted.''
* But if, as these conservatives see it, Reagan decides that four years are enough, then Bush emerges as an acceptable alternative - particularly if Reagan supports Bush, as he probably would.
Even then, however, Bush might face a challenge in the primaries. The first choice of many conservatives is Rep. Jack F. Kemp (R) of New York. Congressman Kemp would have Klein's backing, for example.
But Bush is winning support from more of the conservative movers and shakers. This was evident in the sellout crowd he drew at a Chamber of Commerce luncheon in San Diego recently.
Bush's main problem with conservatives, it seems, comes from the low-profile approach that has made him so acceptable to them as vice-president. Bush's cooperation with Reagan is known. But the fact that he is such a close adviser to Reagan on all issues and that he is so actively engaged in shaping and pushing through the President's programs, is not known. Should this relative political anonymity persist, veteran observers here say, presidential candidate Bush might be vulnerable to a strong challenge.