For three years, Mitchel Sollenberger spent “countless hours” holed up in the Library of Congress, State Department and National Archives reading the letters, biographies and diaries of presidents and Senators.

The resulting book, “The President Shall Nominate: How Congress Trumps Executive Power,” is a look into the prenomination process for federal appointments and the cooperation between the president and Senate.

Sollenberger said he was working at Congressional Research Service, a department of the Library of Congress, when he discovered a need to explore the prenomination process.

When he began his project, he found that most of the research surrounding federal appointments focused on the specific positions or the types of people selected to fill them. There was barely anything on the process itself. Because of this, he was forced to consult diaries and letters for his information, rather than secondary sources.

“My unique contribution is focusing on the process, showing, ‘Look, there is a place for lawmakers in this process,’” Sollenberger said. “There is a history here, and there are ideals and reasons why lawmakers are involved in the process.”

The book breaks down the prenomination process of each president and shows the evolution of the process.

For example, in 1881 during the spoils era — a time when presidents used the spoils system to reward party supporters with government jobs after a successful election — then-Republican President James Garfield became entangled in a conflict with then-Sen. Roscoe Conkling (R-N.Y.) after naming a nominee who didn’t meet Conkling’s approval.

Sollenberger said most scholars would look at this as a case of the president standing up to a Senator and winning. But put in context, the incident was an isolated one. The president and Senator discussed most New York appointments; Garfield just failed to consult Conkling on this particular position.

“It’s a give and take between the presidency and the Congress,” Sollenberger said.

The researcher said the Bush administration actually has consulted more with the minority party during the prenomination process than some past administrations. Bush has commonly consulted with Sens. Charles Schumer (D-N.Y.) and Dianne Feinstein (D-Calif.) on federal appointments in their respective states, for instance, Sollenberger said.

However, he said though it is more prevalent than in the past, the president’s consulting of Senators from his party still is much more common.

In showing differences among the eras and presidents, Sollenberger said he has tried to highlight the importance of remembering that despite the circumstances surrounding the prenomination process, the process itself is still the same.

Now Sollenberger said he is working on a book about the full process of judicial appointments. He said he doesn’t expect the research to take nearly as long, though it will still require some work.

“There’s no magic potion to get this stuff,” he said. “You just have to do the grunt work before writing it.”