In a campaign season haunted by the specter of billion-dollar deficits, many presidential candidates are being forced to respond to questions about how they would balance the federal budget. Since announcing a plan to raise taxes would be a political kiss of death, the candidates are looking for less painful alternatives.

One of the most popular plans for balancing the budget without using the dreaded T-word is the passage of a constitutional amendment granting the president line item veto authority. With this power, the chief executive would be able to veto single appropriations in a spending bill which he deems wasteful and unnecessary without wiping out the entire bill.

So far, several candidates, including Vice President George Bush, Sen. Robert Dole (R.-Kas.), and Massachusetts Gov. Michael Dukakis have joined with President Reagan in favoring use of the line item veto to reduce the deficit. Bush has even included the item veto in one of his campaign commercials, saying that "Congress is against the line item veto. That means it's probably a pretty good idea."

While the majority of Congressmen are opposed to the line item veto, there are a few, including Sen. Edward M. Kennedy (D.-Mass.) and Sen. Joe Biden (D.-Del.), who feel that the authority is a legitimate way to reduce the deficit.

Although the power has never been granted to the president, the item veto is commonly used in the United States. Forty-three states give governors item veto authority, and Congress has, in the past, granted the authority to the governors of many American overseas territories.

The logic behind a line item veto is simple. By putting the entire federal budget into a single omnibus spending package, which the president must ratify in its entirety or veto (thereby shutting down the complete federal bureaucracy), legislators can insert a number of pork-barrel expenditures to please their constituents and improve their re-election chances. That is simply the nature of the legislative beast.

The pork-barrel expenditures included in the last omnibus spending bill, signed just before winter recess, range from the slightly humorous--$240,000 for a study of the damage done to macademia nuts by rats--to the seriously expensive--$25 million for an unneeded new airport in Fort Worth near the home territory Speaker of the House Jim Wright. In the several-thousand pages of an omnibus appropriations bill, these expenditures can be shielded from constituents, and congressmen can hide their support for these perks by claiming that they voted for the whole package, not individual appropriations.

If the president exercised item veto power, it is unlikely that legislators would override the veto and openly support such ridiculous expenditures on their own.

While a line item veto may work on the state level, it is highly unlikely that a president would ever get to use it on the federal level. Constitutional amendments are extremely rare, and there is far from a consensus in support of the item veto.

Opponents of the authority fear that it would be an unnecessary expansion of presidential power. A president with the power to veto individual appropriations could slash his opponents' favorite programs and leave intact his supporters' plans. Fearing for their re-election chances, legislators could become completely subservient to the executive.

And there is no guarantee that the veto would actually reduce spending. If a president wanted a program badly enough, he could blackmail congressional leaders into supporting him by threatening to veto their pet bills. The budget would then include the president's agenda as well as the Congress's.

Since the president is already granted a general veto power by the Constitution, the item veto is unnecessary. With the authority he already has, a shrewd president can expose legislative big spenders and cut out the fat on spending bills--without completely realigning the relationship between the executive and legislative branches.

If an omnibus appropriations package is too wasteful, the president can pick out the most superfluous expenditures and veto the entire bill because of them. Then he could promise to sign the same bill into law, as long as the offensive appropriations were excluded.

Framing the debate in this way, the president could force Congress into the court of public opinion. With a two-thirds majority, Congress could override his veto and pass the original appropriations bill, which would appear to the public as sanctioning wasteful spending. Or they could accept his veto and pass the same bill without those expenditures, as the president had proposed.

Although Congress could override president's veto if his demands were unfair, it is unlikely that two-thirds of Congress would be willing to vote for a package that appeared wasteful unless they could justify all of the expenditures. Threatened with a shut-down of the government because no funds had been appropriated, Congress would have to pass the bill the president wanted.

For all of Reagan's rhetoric about how Congress has stuffed omnibus spending packages--charges that often ring true--the president has signed the giant omnibus packages and vetoed only a handful of smaller appropriations bills. The result has been enormous budget deficits.

Because Reagan has not used his general veto power effectively, the next president will have to.