While the main scandal was the break-in and cover-up, there were other things going on that could have, on their own, been major scandals. Iffy campaign contributions, Agnew's tax evasion and misuse of the FBI and IRS are a few examples. So, if the break-in is unnoticed, one could see the later years of Nixon's administration still mired in scandal, though probably without resignation and an impeachment proceeding. In any case, 1973 is going to be marred by the Agnew tax evasion matter, which was completely independent of Watergate and involved conduct by Agnew that occurred before he became VP.