In 2004, when Senate Republicans were threatening to end Democrats' filibustering of judicial nominees by implementing "the nuclear option," Kennedy called Mr. Caro "out of the blue" and asked if he would come to Washington, D.C., and explain to the freshman senators the importance of preserving the filibuster. After their joint lobbying effort succeeded, Kennedy asked Mr. Caro to introduce him for a speech at the 2004 Democratic National Convention.I agree, that's a foolish speech in hindsight, but I'm not sure we can take this at face value.
Here's the thing. Caro says his books are about power, and he is well known for having an extremely realistic view of how power actually operates in this country. His portrayals of Johnson and Robert Moses are utterly unsentimental. And while he eventually concludes that Moses was a monster who devastated New York, he is grudgingly respectful of Johnson's Great Society accomplishments, even though on the way he betrayed some of his best friends, repeatedly broke the law, stole elections, used government contacts to make himself rich, and so on. One of the most important things Johnson did, actually, was rewrite the Senate rules on seniority to give himself more power and make the body more functional (so that he could accomplish more).
Check out the next graf of that profile:
In exchange, Kennedy offered to help Mr. Caro with the book. Mr. Caro recounts: "I said, 'If you really want to help me, you can get the instructions from your  campaign headquarters about what you did in the different states.'" John Kennedy's presidential campaign had sent Teddy, a 27-year-old political neophyte, to the Western states to win over delegates. Why? "Because they thought it was lost." To his credit, Kennedy delivered the instructions.So Kennedy got Caro to help maintain his power in the Senate, and in return Kennedy helps him with some important documents. Did Caro really believe what he was saying, or was he engaging in a bit of logrolling? I find it hard to believe that he at least wouldn't have understood the subtext. I haven't seen him pressed on this point, but I find it very hard to believe that if he were faced with the standard argument against the filibuster he wouldn't concede the point. Anyone know of an interview with that question asked?