A witty line, an emotional moment or a glaring error can be the difference between winning a high-stakes presidential debate and losing. These unpredictable, nationally televised events can reshape the contours of a campaign and vault a candidate toward victory. Here’s proof:

1960 Richard Nixon vs. John F. Kennedy

Richard Nixon sweated under the hot lights during the debate — the first to be televised — with John F. Kennedy. Polls showed them tied leading up to the debate. Immediately after it, Kennedy was ahead by 3 percentage points.

1976 Gerald Ford vs. Jimmy Carter

“There is no Soviet domination of Eastern Europe,” President Ford said at a time when there certainly was. “I’m sorry, what?” the moderator asked. After the debate, Georgia Gov. Jimmy Carter’s lead expanded to 6 percentage points.

1984 Ronald Reagan vs. Walter Mondale

Asked if, at 73, he was too old to be re-elected, President Reagan said, “I am not going to exploit, for political purposes, my opponent’s youth and inexperience.” Even Walter Mondale laughed as his chances of an election win evaporated.

1988 Michael Dukakis vs. George H.W. Bush

If your wife was raped and murdered, Massachusetts Gov. Michael Dukakis was asked, would you support the death penalty for her killer? He said no. His support was 49 percent before the debate and 42 percent the day after.

1992 Ross Perot vs. George H.W. Bush vs. Bill Clinton

Americans thought third-party candidate Ross Perot won the first and third debates over Vice President George H.W. Bush and Arkansas Gov. Bill Clinton. Perot’s support soared from 10 percent to 17 percent.

2000 Al Gore vs. George W. Bush

Vice President Al Gore sighed repeatedly when Texas Gov. George W. Bush spoke and left his podium to come within inches of Bush. Before the debates, Gore led Bush by 8 percentage points; after them, Bush had the lead and held on to it.