A few days into the campaign for United States Senate in New Jersey, the Republican candidate, Thomas H. Kean Jr., called a news conference in Newark to declare that the integrity of his opponent, Robert Menendez, was a nail he would hammer.

For starters, he scoffed at a claim of early civic virtue by Mr. Menendez, the current senator and the Democratic nominee.

In particular, Mr. Kean said that Mr. Menendez had distorted his own role in the political corruption of Union City, the Hudson County community where Mr. Menendez came to public life 30 years ago as a protégé of an old-fashioned political boss, William V. Musto.

Mr. Kean said that while Mr. Menendez now poses as a brave truth teller who helped topple a regime of political crooks, he had actually issued $2 million in public money to a corrupt contractor "as part of a massive illegal kickback scheme." Had Mr. Menendez not cooperated with prosecutors, aides to Mr. Kean said, he might have gone to jail himself.

To a depth unusual for events that are decades old, the Kean campaign's accusations can be measured against a robust historical record — including F.B.I. tapes and volumes of trial testimony — of a roiling human and legal drama between 1978 and 1982 in Union City.

The Kean accusations find no support in those records or from independent authorities of that era.