Ask any self-respecting Congressional staffer how life on the Hill has been, and the usual response would be: “Busy.—

That’s certainly true for David McKean. As staff director of the Senate Foreign Relations Committee, his workday revolves around managing a staff of 25, setting up hearings (12 so far this session), and scouting for experts to testify.

As if his hands are not already full, McKean is also promoting his third book, “The Great Decision: Jefferson, Adams, Marshall, and the Battle for the Supreme Court.—

McKean also wrote the 1994 book “Friends in High Places: The Rise and Fall of Clark Clifford,— about the influential Truman aide, and the 2004 book “Tommy the Cork: Washington’s Ultimate Insider from Roosevelt to Reagan,— about Thomas G. Corcoran, one of the first modern lobbyists.

How did he find time to write “The Great Decision— in the first place?

“I did a fair amount of writing at night … and on weekends, mostly,— McKean said in an interview at the Dirksen Senate Office Building.

When McKean started writing “The Great Decision— in 2006, he was chief of staff for Sen. John Kerry (D-Mass.), a position he had held since 1998. When Kerry became the 111th Congress’ Senate Foreign Relations chairman, he appointed McKean as committee staff director.

McKean said the most difficult part about writing his third book was not the research or the writing. “It’s finding the time to do it,— he said. “It helps to have a co-author.—

That co-author is Cliff Sloan. McKean and Sloan have known each other for more than three decades, having been roommates at Harvard College.

A partner at Skadden, Arps, Slate, Meagher & Flom, one of the District’s largest law firms, and a former law clerk to Supreme Court Justice John Paul Stevens, Sloan had wanted to write a book about the Supreme Court.

“And then he thought, Maybe that’s a little bit too ambitious,’— McKean said. Instead, Sloan figured he’d think about when the court became a “significant leg— in the stool of the three branches of government, McKean said.

So McKean and Sloan looked at the landmark case of Marbury v. Madison. The Supreme Court decision in Marbury is touted to be “one of the cornerstones of the American constitutional system,— he said.

Marbury established the Supreme Court — an insignificant component of government in the 1800s — as the branch that would have the final say on “what the law is.— The case also set the court’s authority to strike down a law as unconstitutional.

In the course of writing the book, he said he bought a lot of secondhand books for his research. He and Sloan also spent countless hours at the Library of Congress and the National Archives.

The Archives has the Marbury case on display along with other original documents that have defined America’s fundamental values, namely the Declaration of Independence, the Constitution and the Bill of Rights.

This explains why “The Great Decision— authors chose the Archives as the venue of their book discussion and signing last week. “This impressive building houses the nation’s documents … the ties that bind America,— McKean told the audience.

In his speech, McKean underscored the significance of the Marbury case and story behind the legal opinion. The story of the Marbury case has all the elements of a compelling drama. The cast of characters includes former presidents John Adams and Thomas Jefferson, as well as John Marshall, the third chief justice of the United States.

During Adams’ first term as president, Jefferson was his vice president. When Adams sought re-election, he lost to Jefferson. Days after his inauguration, Jefferson was angered to learn that as Adams was “packing his bags to leave the White House, he was also packing the federal government with Federalist appointees,— McKean said.

One of Adams’ “midnight— appointees was William Marbury, whose presidential commission as a justice in Washington County was blocked by Jefferson. Marbury was not able to take office. So he sued Jefferson and his secretary of state, John Madison, before the Supreme Court.

Marshall had been Adams’ secretary of state before becoming chief justice. He was also Jefferson’s cousin and the former president despised him.

How the Supreme Court arrived at “the great decision— is something McKean and Sloan succeed in telling. The Marbury case is so rich in messy personal contacts that learning about it from a general history is not enough.

“The Great Decision— also highlights the parallelism between the political scene in the 1800s and that of recent times, such as the deadlock in the presidential election, the complaints of partisan media and the selection of judges and justices.

“Most people, when they hear a law case, they are not sure about how interesting it’s going to be. And so I think the challenge for us is to tell a good story and to keep it interesting,— McKean said. “I feel as though we succeeded pretty well in that.—

With “The Great Decision— now out on the shelves, McKean is juggling time between legislative work and book tours.

Last Saturday, he and Sloan did a book signing at Politics and Prose bookstore on Connecticut Avenue. This week, McKean will oversee hearings on the global financial crisis, alleviating global hunger and the nomination of State Department diplomats.