[SunkenCiv]

Heh, I think he was in Congress long enough that, when he coined that one, it was million instead of billion. 😁

[Albion Wilde]

There is a "Dirksen Congressional Center" online that claims to have access to his papers, and they can't find absolute confirmation that he said it as quoted; but they did confirm that he said "billion" in similar contexts. Here is a relevant passage from their website:

The chief evidence in support of Dirksen making the statement comes from people who claim to have heard him. The Library of Congress, for example, cites someone's personal observation on the campaign trail as evidence. The Dirksen Center has received calls from people who heard Dirksen say those words, some even providing the date of the event. But cross-checking that information with the records has, so far, turned up nothing in the way of confirmation.

The closest documented statement came at a joint Senate-House Republican leadership press conference on March 8, 1962, when Dirksen said, "The favorite sum of money is $1 billion – a billion a year for a fatter federal payroll, a billion here, a billion there." [EMD Papers, Republican Congressional Leadership File, f. 25] But the "and pretty soon you're talking real money" is missing....

Of course, the Dirksen Papers do not document completely the late Senator's comments....