It has happened again. Just when it appears that the Reagan administration is finally about to be conveniently typed and pegged - and the current media view seems to be that of a ''conservative'' administration given to admiration of the Coolidge years - the administration pops up with a new proposal that quickly shatters the stereotypes and reminds everyone how ''activist'' this new President can be. What for example, would FDR or Harry Truman have made of Mr. Reagan's latest bold bid in the presidential power area - urging that presidents be given the authority to veto specific line items in the federal budget?
Currently, a president can only veto an entire piece of legislation. Congress , by a two-thirds vote, can override that veto. Mr. Reagan, however, seeking to extend his authority over the federal budget process, would like authority to veto specific provisions in appropriations bills. Many governors have greater power over state budgets than the president has over the federal budget.
A line-item veto, according to many legal scholars, would require a constitutional amendment. That, of course, would mean a long and presumably grueling battle at the state legislative level. And there is little sympathy on the part of Congress for such an obvious diminution in its powers.
Yet should the idea - and an administration spokesman suggests that it is mainly a ''generalized wish'' at this time - be simply dismissed out of hand? Part of the difficulty in enacting federal budgets each year is that lawmakers cunningly play the game of ''loading'' budget bills with all sorts of expensive ornaments. That is, myriad amendments, some patently objectionable, many geared only to special-interest groups, are deliberately tacked onto appropriation bills. By such measures lawmakers in effect are daring or, in some cases, inviting vetoes. This is hardly a responsible or forthright way of passing money measures on their merits.
Like Mr. Reagan's decision last week to end-run the budget process by seeking to ''defer'' spending on projects unless overruled by at least one branch of Congress, the line-item proposal once again shows the Reagan White House willing to consider an innovative, even audacious, approach to presidential power. It is true that the Constitution specifically grants authority over spending bills to Congress (starting with the House). But it must not be forgotten that the modern budget process itself started, perhaps fittingly, with a conservative Republican business-oriented administration back in 1921, with the establishment of the Bureau of the Budget in the executive branch. This administration would certainly have precedent for proposing changes in the budget process.
Many questions will have to be asked by both lawmakers and constitutional authorities about the wisdom of a line-item veto. Would it serve the national interest? A solid debate on the concept seems in order, starting with Congress itself.