If President Clinton testifies before the grand jury investigating the current White House scandal, he would set a legal precedent - but he would hardly be the first president ever to bear witness under oath.
Other presidents, from Thomas Jefferson to Richard Nixon, have been called to provide information to investigators.
Ronald Reagan, after leaving the White House, gave video testimony in the Iran-Contra trial of national security adviser John Poindexter.
Even Mr Clinton himself has already testified twice via videotape in trials stemming from an independent counsel probe of the 1980s Whitewater land deal in Arkansas. And he made a sworn statement last January in the Paula Jones sexual harassment case against him.
But neither Mr Clinton nor any other president has gone before a grand jury, where witnesses' attorneys are forbidden, to answer questions from prosecutors and jurors about a scandal that centres on his own alleged behaviour.
His legal team has been negotiating with Mr Starr to try to keep this precedent unbroken, even after being served with a grand jury subpoena for the president's testimony.
Mr Clinton's private attorney, Mr David Kendall, said in a statement that he would work with the independent counsel, Mr Kenneth Starr, "to devise a way for the president to provide information for the . . . investigation, consistent with his constitutional role and responsibilities".
Since January, Mr Starr's grand jury has been investigating allegations that Mr Clinton illegally tried to cover up an affair with Ms Monica Lewinsky, a former White House intern. That panel has heard from White House functionaries, Secret Service agents, Ms Lewinsky's mother and her erstwhile friend, Ms Linda Tripp, but so far Ms Lewinsky and Mr Clinton have stayed away.
"[Mr Clinton] probably has to give some kind of testimony, whether he does it by going in to the grand jury or by giving videotaped testimony at the White House," said Prof Robert Shapiro, an academic who specialises in presidential leadership at Columbia University in New York.
There are risks to either option, Prof Shapiro acknowledged in a telephone interview, but said that in any case, "for a prosecutor to have a president obeying commands is something that would seem to be demeaning and a black mark on the presidency". And it would also be damaging to fight the subpoena, Prof Shapiro said.
Mr Clinton's testimony would raise a question that has been debated among constitutional scholars for months: whether any president can be compelled to testify before any grand jury.
Lawyers who support the Clinton camp argue that the constitutional separation of powers precludes a grand jury from any jurisdiction from calling presidents to account; the proper forum for this would be Congress, which could invoke the articles of impeachment, possibly leading to a president's ouster.
But Mr Starr and attorneys who line up with Mr Starr's team have maintained throughout the Lewin sky investigation that the president is not above the law.
They draw support for this position from a 1997 Supreme Court ruling that found Mr Clinton could be compelled to testify in the Jones case while he was in office. That case against Clinton was dismissed in April but is expected to be appealed.
While the subpoena appears to put Mr Clinton in a tight corner, one expert on the presidency, Dr Colin Campbell of Georgetown University, said public opinion will probably figure heavily in the final analysis.
"This presidency on the level of personal probity has been assailed almost from the beginning," Dr Campbell said. "He has shown a tremendous capacity for these types of attacks to just slide right off his back."