WASHINGTON (CNN) -- As part of intensive preparations for upcoming congressional questioning concerning the eight fired U.S. attorneys, Attorney Gen. Alberto Gonzales will undergo mock sessions next week in which he takes part in practice questions and answers which could include outside legal advisers, Justice Department officials say.

The attorney general, who has not had any public events this week and has remained behind closed doors at the Justice Department, cancelled plans for a family vacation in order to spend time on his preparations, officials say.

Several Republican political consultants, who requested anonymity since they were talking about the future of the attorney general, have told CNN that what Gonzales tells congress in the next few weeks and how he is received will be key to whether he can rebuild support on Capitol Hill.

"He has a tall order," is how one of them put it, saying it has to be a "compelling presentation."

The preparation Gonzales is doing is similar to what a cabinet nominee undergoes before a confirmation hearing.

Justice Department officials acknowledge the importance of the Attorney General's testimony before the Senate Judiciary Committee on April 17.

To help bolster his lagging support, the Attorney General is continuing "to reach out" to Capitol Hill, a Justice Department official said. The official said so far Gonzales has spoken to more than a dozen GOP members of Congress and added he may speak to some Democrats as well.

He is sure to face many questions from both sides of the aisle on inconsistencies in the accounts of what his role was in the firing of the prosecutors and demands for more specifics on his actions. Gonzales has said he knew little about the discussions concerning the dismissals, whereas his former chief of staff, Kyle Sampson, testified last week that Gonzales was continually briefed on the matter.

Previewing some of the questions to come, Senate Judiciary Chairman Patrick Leahy, D-Vermont, Thursday sent a letter to the attorney general asking him to include in his prepared testimony "...a full and complete account of the development of the plan to replace United States attorneys, and all the specifics of your role in connection with that matter."