Ken Starr had no broad mandate to investigate anything he wanted to. His mandate was Clinton and Whitewater, nothing else and certainly not like Mueller who is going all over the place and into issues that have nothing to do with Trump and collusion. Starr's concern was when he stumbled on the Lewinsky matter. In an article in Time dated Jan 9th, 2009 Starr said: "All in all, it would have been better, more prudent for a different independent counsel to be appointed to investigate the Lewinsky phase of the investigation, but I think that is wishful thinking. "It had to be investigated under the [independent counsel] statute. The statute required that if certain information came to the attention of the attorney general, then the matter had to be investigated and Attorney General [Janet] Reno did her duty and said the Lewinsky matter has to be investigated and the sitting independent counsel should be the one to do it".
Yeah, Rosenstein added one additional memo of guidance after what happened had already been done. I believe it was about when Mueller sent in Federal agents to Manafort's home in the dead of night.
They were all things that happened years ago, before Trump decided to run for the presidency. It's Mueller only exceeding his mandate. Starr on the other hand kept to Clinton, no one else until the Lewinsky matter and it was AG Reno who told him to go there. Not so in this case, Rosenstein is only the rubber stamp for what Mueller wants to do.
As you can see, the investigation of president Clinton did branch out into areas unrelated to the original issue. It lasted 5 YEARS from the appointment of the initial Special prosecutor to the trial in the Senate.
Your claim about the Mueller investigation being different is obviously incorrect. The appointment of Mueller as Special Council was just about a year ago (May 16, 2017). So for this investigation to be as extensive as the Clinton investigation it should go on for another 4 YEARS.
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Clinton impeachment timeline
January 1994
Attorney General Janet Reno appoints Robert Fiske Jr. as the independent counsel in charge of investigating financial irregularities in the dealings of the Whitewater property company. The Clintons, and their business partners, James and Susan McDougal, are implicated.
August 1994
Fiske is replaced by the more conservative Kenneth Starr as the independent counsel investigating the Whitewater scandal.
May 1996
The first Whitewater trial ends with the conviction of the McDougals for fraud. A Senate hearing ends inconclusively a month later.
February 1997
Kenneth Starr, the Independent Counsel investigating the Whitewater scandal, announces he will step down from the investigation.
He then changes his mind and continues his investigations.
May 1997
According to the Starr report released in September 1998, President Clinton tells Ms Lewinsky the affair is at an end. Just days later the Supreme Court reject Mr Clinton's claim that as President he should have immunity from civil cases. This ruling allows the Paula Jones harassment case to proceed against him.
January 16, 1998
Janet Reno, the US Attorney General, approves the Whitewater independent counsel Kenneth Starr's request for an
expansion of the inquiry to include the Clinton-Lewinsky affair.
March 13, 1998
Paula Jones' lawyers in the sexual harassment suit against Clinton publish much of their evidence, one of the many breaches of the judicial gagging order on this case.
April 1, 1998
The Paula Jones harassment case against the President is dismissed by the judge before it goes to trial.
September 8, 1998
Attorney-general Janet Reno announces a 90-day inquiry into whether Bill Clinton helped to plan a $44 million Democratic Party "issue ad" that breached election campaign spending laws.
September 9, 1998
Independent Counsel Kenneth Starr releases his report to Congress. It has 11 possible grounds for impeachment. The House votes to make the 445-page report public.
October 5, 1998
The House Judiciary Committee votes to launch a congressional impeachment inquiry against President Clinton.
October 8, 1998
The House of Representatives vote for impeachment proceedings to begin against Clinton. The House judiciary committee will be given wide powers to draw up detailed charges against Mr Clinton, based on 11 allegations by the independent counsel Kenneth Starr in his report on the Monica Lewinsky affair.
December 1, 1998
The House of Representatives judiciary committee widens the scope of its inquiry to include the election campaign fundraising issue. The Republicans use their majority on the committee to subpoena senior law enforcement officers, including the FBI director Louis Freeh, to broadening the impeachment inquiry into a dispute over President Clinton's campaign fundraising.
December 11, 1998
The House Judiciary Committee approves three articles of impeachment on a 21-16 party line vote, passing them to the full House of Representatives. The three articles accuse Clinton of lying to a grand jury, committing perjury by denying he had sexual relations with Monica Lewinsky, and obstructing justice. Clinton declares himself "profoundly sorry" and willing to accept censure.
December 12, 1998
The committee approves a fourth article of impeachment on a party-line vote, accusing Clinton of abusing power in a direct parallel to Watergate-era language.
December 19, 1998
President Clinton is impeached as the Republican controlled House approves two of the four proposed articles of impeachment by narrow partisan majorities: 228-206 and 221-212. Mr Clinton is sent for trial in the Senate.
January 7, 1999
The Senate formally begins the impeachment trial of President Bill Clinton on two charges of perjury and obstruction of justice.