What made Nixon change his mind about resigning?

Nixon had a meeting with senior ranking Republican Barry Goldwater on August 7, 1972; also at the meeting were Senate and House leaders Hugh Scott and John Rhodes. They informed him he didn't have the support in Congress to avoid a trial; he faced full impeachment and certain conviction. Nixon finally saw the writing on the wall and realized resignation was his only option.

The following day, Nixon announced to the nation he was resigning at noon on August 9.

The previous poster provided a good account of the internal meetings with fellow Republicans prior to the resignation.

This might clear up some of the timeline. Note that according to this, as late as August 6th, Nixon said he would not resign.

Assuming the movie paid close attention to the actual dates, and everything I've read and heard said they tried to get the details as close as possible, this is what the movie said.

The final scene(s) start in the newsroom and we see a television, broadcasting Nixon's 2nd Inauguration, January 20, 1973.

It then switches to the teletype and all these have the date in the heading:

JANUARY 11,1973 (Nine days before the inauguration)
HUNT PLEADS GUILTY TO THREE COUNTS OF CONSPIRACY, BURGLARY, . . .

AUGUST 17, 1973
MACGRUDER PLEADS GUILTY TO HELPING PLAN WATERGA......

It continues with dates from 1973 and into 1974 with lines about various pleas entered by Nixon staffers and others.

It jumps to 1975 to show what happened to some of the bigger names like Mitchell, Haldeman, etc.. Then the last two:

AUGUST 6, 1974
TAPES SHOW NIXON APPROVED COVER-UP. PRESIDENT SAYS HE WON'T RESIGN.

AUGUST 9, 1974
NIXON RESIGNS.
GERALD FORD TO BECOME 38TH PRESIDENT AT NOON TODAY