Don't recall that--Segretti, perhaps? Anyway, he didn't appear, and no one has yet raised a single example where a sitting President did.
He WAS subpoened, and spun, delayed and tread water for a couple of months, then faced with the reality that he was caught cold, he resigned.
~~~~
Watergate Chronology
1974
January
There are now ongoing calls for Nixon to resign and the Congress begins to seriously consider impeachment.
TIME Magazine names Watergate Judge John Sirica as Man of the Year.
February 6
The House of Representatives votes to authorize the House Judiciary Committee to investigate whether grounds exist for the impeachment of President Nixon.
Complete List of Members of the House Judiciary Committee
March 1
Nixon is named as an unindicted co-conspirator in an indictment against seven former presidential aides.
April 16
Special Prosecutor Jaworski issues a subpoena for 64 White House tapes.
April 30
Nixon refuses to hand over the tapes, but provides more edited transcripts to the Judiciary Committee. He appears on national television to announce his decision to release the transcripts. There is public shock at the general tone of the conversations and the foul language used by Nixon and others. The expression “expletive deleted” enters the vocabulary.
Full Text of Nixon’s Address to the Nation.
May 9
Impeachment hearings begin before the House Judiciary Committee.
July 24
The Supreme Court, by a unanimous vote of 8-0 (William Rehnquist abstaining) upholds the Special Prosecutor’s subpoena, ordering Nixon to make the tapes available for the Watergate trials of his former subordinates. The case is known as United States v. Nixon.
The full text of the Supreme Court’s decision.
Listen to some of the White House tapes.
July 25
Barbara Jordan, a Democratic Party member of the House Judiciary Committee, makes a famous speech reminding her colleagues of the constitutional basis for impeachment of the President.
Read Barbara Jordan’s speech
July 27
The House Judiciary Committee adopts the first Article of Impeachment by a vote of 27-11, with 6 Republicans voting with the Democrats. The Article charges Nixon with obstruction of the investigation of the Watergate break-in.
Full text of the Articles of Impeachment.
Analysis of the Judiciary Committee’s votes.
Listen to the announcement of the Committee’s vote to Chairman Rodino.
Listen to Lawrence Hogan, a Republican member of the Committee
July 29
The House Judiciary Committee adopts the second Article of Impeachment that charges Nixon with misuse of power and violation of his oath of office.
July 30
The House Judiciary Committee adopts the third Article of Impeachment, charging Nixon with failure to comply with the House subpoenas.
Listen to the Impeachment Resolution being moved in the Judiciary Committee
August 5
Nixon releases transcripts of three conversation he had with Haldeman six days after the Watergate break-in. The June 23 tape becomes known as The Smoking Gun because it reveals that Nixon ordered the FBI to abandon its investigation of the break-in.
Nixon releases three more tapes that prove he ordered a cover-up of the Watergate burglary on June 23rd 1972, six days after the break-in. The tapes show that he knew of the involvement of White House officials and the Campaign for the Re-election of the President, as well as revealing that Nixon ordered the FBI to abandon its investigation of the break-in.
These tapes become known as The Smoking Gun The eleven Republicans on the Judiciary Committee who voted against impeachment say they will change their votes. It is clear that Nixon will be impeached and convicted in the Senate.
Transcript of the Smoking Gun tape
August 7
Three senior Republican congressmen meet with Nixon, advising him that his chances of avoiding impeachment by the House and removal from office by the Senate are “gloomy”.
Around the country, calls mount for Nixon’s resignation, and speculation builds about Nixon’s intentions.
A Law Professor at the University of Arkansas comments on Watergate.
August 8
In a televised address to the nation at 9pm, Nixon announces that he will resign
http://watergate.info/chronology/1974.shtml
(links active at site)
On this day in 1998, President Bill Clinton becomes the first sitting president to testify before the Office of Independent Council as the subject of a grand-jury investigation.
http://www.history.com/this-day-in-history/clinton-testifies-before-grand-jury