Nice Work If You Can Get It : One President falls ill and another fills the void : FATHER’S DAY, <i> By John Calvin Batchelor (Henry Holt & Co.: $23; 528 pp.)</i>

Novels about political conspiracies of the peculiarly American kind are usually set in the indefinite future lest their plots be overshadowed by events such as Teapot Dome or Watergate or the Iran-Contra mess.

But John Calvin Batchelor has set “Father’s Day,” his intriguing novel of truly grand political conspiracies, in early 2003, which is slightly more than two years after the Democrats have again won not only the White House but also overwhelming majorities in the Congress.

However, the Democrats have a slight problem despite their victory. Although Theodore G. Jay, the former governor of Michigan, was elected the nation’s 43rd President, and former Sen. T. E. Garland of Texas its vice-president, Jay’s approval ratings have hit a post-Cold War low. And Jay himself has collapsed with “a disability diagnosed as a major depressive episode” and been carried off to Walter Reed hospital. This leaves the nation--under the provisions of the 25th Amendment--with its first acting President, T. E. Garland.

The new acting President is one of those cunning, larger-than-life Texans who might be a parody had we not already been blessed with so many of them--from Texas Jack Garner, F.D.R.’s first vice-president, to Lyndon Johnson to the redoubtable Ann Richards, governor of the Lone Star State.

Garland indeed happens to be a nephew of L.B.J. and had sought his party’s nomination for himself only to be defeated in the primaries by President Jay. But no one deep down really wants to be vice-president and we learn almost immediately that Garland, with the help of those two reliable political retainers, fair means or foul, is determined that the disabled Jay will never move back into the White House.

The fair means would require strict adherence to the 25th Amendment. Its legal niceties provide that a disabled President’s right to resume office can be successfully challenged by the acting President if this challenge is supported by the Cabinet and a two-thirds majority in both houses of Congress.

Garland is convinced he has these votes in his pocket. But just in case, there is a foul means fall-back that would result in Jay’s assassination. The problem, as always, is where does one find a reliable assassin?

In far-off Moldova is where--in that former constituent republic of the Soviet Union, bordering on Romania until the breakup of the U.S.S.R. Now it’s an independent republic occupied in part by the U.S. Army’s 10th Mountain Division. The designated assassin in Lt. Col. George M. “Red” Schofield, commander of the First Battalion of the division’s 14th Regiment.

The assassination plot calls for much of the battalion to be secretly air-lifted back to the United States. There it will land, create a diversion and overpower the President’s Secret Service detail. Colonel Schofield will then pull the trigger of the gun that kills the President. And this is exactly what he does in the novel’s first chapter--except it’s a mock raid on a mock president carried out at Fort Chaffee, Ark.

After the raid, the chairman of the Joint Chiefs of Staff, Gen. Lucius S. Sensenbrenner, congratulates the Lieutenant Colonel and adds, “We’re changing the designator for this operation from CAR ALARM to FATHER’S DAY. Don’t think about it too hard. The go code is ‘Happy Father’s Day.’ Understood?”

The Colonel understands and it appears that acting President Garland has not only the Congress and the Cabinet in his pocket, but also the Army, the Navy, the Air Force, the Marines and the Joint Chiefs of Staff. The military, it seems, is enraged because the defense budget has been slashed to a point where bullets are rationed, noncoms are on food-stamps and U.S. military might is a ghost of what it once was.

In fairness, it should be pointed out that the decline in the military’s fortunes might not be entirely the fault of Jay, the disabled President. Batchelor makes him the 43rd President. Since Bill Clinton is the 42nd President, this means that Clinton must have won a second term although Batchelor doesn’t touch on how this was accomplished.

With the Democrats in power but also in disarray and low in the polls, one wonders what the Republicans are doing to take advantage of such a rich opportunity? The answer lies in the state of Maine and its GOP governor, “John Gerry ‘Jack’ Longfellow, Jr., forty-eight, as fleet of sail and sure of tongue as any man ever took the helm of Blaine House at Augusta.” This is Batchelor’s own rather Down East description.

Governor Longfellow happens to be married to Sen. Jean Motherwell (R-Me.), who is the minority leader in the Senate in Washington and titular head of her party. Her husband has hopes of being the next Republican candidate for President. She has hopes of becoming the Senate’s new majority leader. But unknown to her, he is having an affair with the widow of McAndrew Schofield whose baby brother is none other than Col. Schofield of the 10th Mountain Division and the Army’s assassin apparent.

Shortly after this revelation, the supposedly invalid President announces his recovery and demands his job back. This ignites a tale of deadly conspiracy whose participants are an assortment of weird and wonderful characters. Not the least of them is the billionaire sheriff of Yuma County, Ariz., who has his own cable TV show called “Southwest Cooking With Sheriff Gus Keebler.” The Sheriff uses the show to dispense recipes and also political gossip of the most vicious and scurrilous kind.

“Father’s Day” offers a fascinating, if gloomy, vision of the world in 2003. Many of the principal characters seem to spend their waking hours with a cellular phone stuck in their ear, a pandemic scourge whose symptoms are already visible. Then, too, Europe is broke. Africa is lost. The Mideast is a shambles. Cairo has been leveled by an earthquake. The U.S. has two Preisdents. And Wall Street is in a dive. But still the Presidency and its semblance of power remains a job that some would kill for.

Batchelor writes smoothly, has done his research and has an ear for dialogue that’s refreshing. “Father’s Day” may be a plot-driven novel but it’s also the plot of a master.