[1]: 
They cite a pair of articles, the first one being an NYT article titled "Spy Agencies Say Iraq War Worsens Terrorism Threat"
https://archive.fo/jW1S8
Then this LA Times article, "No Room for Doubt in the Oval Office"
https://archive.fo/LN97v
They also quote Frank Rich's book, "The Greatest Story Ever Sold: The Decline and Fall of Truth from 9/11 to Katrina", mostly for it's account of Bush's public claims about the Iraq war:
> On May 25, 2006, with his ratings below 30 percent, Bush finally admitted that he had been wrong about something, sort of. Not about the war or any of the decisions related to it, but about his choice of words. When he used "tough talk" such as "bring it on" and "wanted, dead or alive," Bush said, "I think in certain parts of the world it was misinterpreted."
> In October 2006, shortly before the midterm elections, the White House announced Bush would no longer be using his familiar "stay the course" line because it implied the administration was not "flexible" about Iraq policy. Nonetheless, in a press conference on October 25, with violence in Iraq at record highs, Bush said there would be no major changes in his overall strategy and that he was committed to "getting the job done."
> When asked whether the United States was winning the war, he said, "Absolutely, we're winning."

[2]:
They search for every single instance a president says the phrase "mistakes were made" at the American Presidency Project's website. True to their word, it's quite a list.
https://www.presidency.ucsb.edu/advanced-search?field-keywords=%22mistakes+were+made%22&field-keywords2=&field-keywords3=&from[date]=&to[date]=&person2=&category2[]=&items_per_page=100