WASHINGTON — Senator Robert Menendez told a federal judge on Monday that corruption charges against him should be thrown out because prosecutors trampled on the independence of Congress and unfairly treated campaign donations as crimes.

In hundreds of pages of court documents, Mr. Menendez, Democrat of New Jersey, provides an aggressive response to his indictment in April, in which the Justice Department accused him of trading political favors for luxury vacations, free airfare and campaign donations. He was charged alongside his longtime friend and political benefactor, Salomon E. Melgen, a wealthy Florida eye surgeon.

But much more than the fates of Mr. Menendez and Dr. Melgen are at stake. Their lawyers have made the indictment a test case over how far the Justice Department can go when investigating graft on Capitol Hill. The outcome could have ramifications in corruption investigations for years to come.

Mr. Menendez is the first senator to face federal bribery charges since another New Jersey Democrat, Harrison A. Williams Jr., was indicted in 1980 as part of the federal corruption investigation known as Abscam. In 2002, an ethics scandal deterred Senator Robert G. Torricelli, Democrat of New Jersey, from a re-election bid. And Ted Stevens, Republican of Alaska, was convicted in 2008 of lying about gifts on Senate ethics forms. A federal judge set aside the conviction, citing prosecutorial misconduct.