Donald Trump claimed during the first presidential debate on Monday night that he considered using sordid details of Hillary Clinton's personal life against her, but refrained.

"I was going to say something extremely rough to Hillary and her family, and I said to myself, I couldn't do it. It's inappropriate. It's not nice. But she's spent hundreds of millions of dollars on negative ads against me, many of which are untrue," Trump said. "It's not a nice thing."

Clinton, Trump face off in first presidential debate



34 PHOTOS Hillary Clinton, Donald Trump face off in first presidential debate See Gallery Hillary Clinton, Donald Trump face off in first presidential debate U.S. Secret Service agents walk onto the debate floor before the first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Workers on the stage prepare for the first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Brian Snyder A TV cameraman works during a rehearsal for the first U.S. presidential debate at Hofstra University in Hempstead, New York September 25, 2016. REUTERS/Rick Wilking The media center for the first U.S. presidential debate is seen at Hofstra University in Hempstead, New York, U.S. September 24, 2016. REUTERS/Rick Wilking Ivanka Trump arrives for the first presidential debate at Hofstra University in Hempstead, New York on September 26, 2016. / AFP / Timothy A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) Chris Christie, governor of New Jersey, waves to an attendee in the audience ahead of the first U.S. presidential debate at Hofstra University in Hempstead, New York, U.S., on Monday, Sept. 26, 2016. Hillary Clinton and Donald Trump meet Monday night for a presidential debate that will give them their broadest exposure to voters and promises to be a pivotal moment in a long and increasingly close race. Photographer: Daniel Acker/Bloomberg via Getty Images HEMPSTEAD, NY - SEPTEMBER 26: Republican presidential nominee Donald Trump's wife, Melania Trump greets with Democratic presidential nominee Hillary Clinton's husband and former U.S. President Bill Clinton during the Presidential Debate at Hofstra University on September 26, 2016 in Hempstead, New York. The first of four debates for the 2016 Election, three Presidential and one Vice Presidential, is moderated by NBC's Lester Holt. (Photo by Drew Angerer/Getty Images) Republican candidate for Vice President Mike Pence looks on before the first presidential debate at Hofstra University in Hempstead, New York on September 26, 2016. / AFP / Paul J. Richards (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images) Democratic U.S. presidential nominee Hillary Clinton waves after the first presidential debate against Republican U.S. presidential nominee Donald Trump (not shown) at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Adrees Latif TPX IMAGES OF THE DAY Democratic nominee Hillary Clinton (L) and Republican nominee Donald Trump leave the stage after the first presidential debate at Hofstra University in Hempstead, New York on September 26, 2016. / AFP / Timothy A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) Democratic nominee Hillary Clinton (R) gestures next to Republican nominee Donald Trump during the first presidential debate at Hofstra University in Hempstead, New York on September 26, 2016. / AFP / Timothy A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton speak during their first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Adrees Latif Moderator Lester Holt presides over the first debate between Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Joe Raedle/Pool Melania Trump (L-R), the wife of Republican U.S. presidential nominee Donald Trump, sits with his daughter Ivanka Trump, Republican vice presidential nominee Mike Pence and Pence's wife Karen Pence during Trump's first debate against Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S. September 26, 2016. REUTERS/Jonathan Ernst New Jersey Governor Chris Christie (R) and former New York City Mayor Rudy Giuliani chat as they take their seats ahead of the start of the first debate between Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Mike Segar Dallas Mavericks owner Mark Cuban arrives at the U.S. presidential debate between Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Mike Segar Las Vegas casino magnate Sheldon Adelson sits with his wife Miriam as they await the start of the first debate between Republican U.S. presidential nominee Donald Trump Democratic and U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Promoter Don King Don King (C) speaks with Las Vegas casino owner Sheldon Adelson prior to the first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Mike Segar Former U.S. President Bill Clinton (C) talks with his daughter Chelsea Clinton prior to the first presidential debate between Republican presidential nominee Donald Trump and U.S. Democratic presidential candidate Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. At right is Marc Mezvinsky, the husband of Chelsea Clinton. REUTERS/Carlos Barria Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton speak during their first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Adrees Latif Republican U.S. presidential nominee Donald Trump reacts during the first presidential debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Democratic U.S. presidential nominee Hillary Clinton smiles during the first presidential debate with Republican U.S. presidential nominee Donald Trump at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Brian Snyder Republican U.S. presidential nominee Donald Trump reacts during the first debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Democratic U.S. presidential nominee Hillary Clinton speaks during the first presidential debate with Republican U.S. presidential nominee Donald Trump at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Republican U.S. presidential nominee Donald Trump speaks as Democratic U.S. presidential nominee Hillary Clinton looks on during their first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Republican U.S. presidential nominee Donald Trump speaks during the first presidential debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Debate moderator Lester Holt of NBC News replaces his jacket after a technician fixed his earpiece before the first debate between Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S. September 26, 2016. REUTERS/Jonathan Ernst Republican U.S. presidential nominee Donald Trump pauses during the first debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Lucas Jackson Democratic U.S. presidential nominee Hillary Clinton and Republican U.S. presidential nominee Donald Trump speak during their first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Adrees Latif Republican U.S. presidential nominee Donald Trump and Democratic U.S. presidential nominee Hillary Clinton discuss a point during their first presidential debate at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Joe Raedle/Pool Donald Trump, 2016 Republican presidential nominee, speaks during the first U.S. presidential debate at Hofstra University in Hempstead, New York, U.S., on Monday, Sept. 26, 2016. Hillary Clinton and Donald Trump meet Monday night for a presidential debate that will give them their broadest exposure to voters and promises to be a pivotal moment in a long and increasingly close race. Photographer: Andrew Harrer/Bloomberg via Getty Images Democratic U.S. presidential nominee Hillary Clinton pauses during the first presidential debate with Republican U.S. presidential nominee Donald Trump at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Joe Raedle/Pool Republican U.S. presidential nominee Donald Trump sips water during his first debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Joe Raedle/Pool Republican U.S. presidential nominee Donald Trump (2nd from L) chats with members of his family after the conclusion of his first debate with Democratic U.S. presidential nominee Hillary Clinton at Hofstra University in Hempstead, New York, U.S., September 26, 2016. REUTERS/Adrees Latif Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Trump later reiterated to Yahoo News reporter Hunter Walker in the spin room he was indeed tempted to bring up former President Bill Clinton's decades-old extramarital affairs.

"I was, but I decided not to do it out of respect for Chelsea," the Republican presidential candidate said, referring to Chelsea Clinton, the Clintons' daughter.

The comments came after the Republican presidential nominee defended his assertion that Hillary Clinton does not have a "presidential look."

Pressed by moderator Lester Holt, Trump doubled down.

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