Through all time to come, I think America will be a stronger nation, a more just society, and a land of greater opportunity and fulfillment because of what we have all done together in these years of unparalleled achievement.
Our reward will come in the life of freedom, peace, and hope that our children will enjoy through ages ahead.
What we won when all of our people united just must not now be lost in suspicion, distrust, selfishness, and politics among any of our people.
Believing this as I do, I have concluded that I should not permit the Presidency to become involved in the partisan divisions that are developing in this political year.
With America's sons in the fields far away, with America's future under challenge right here at home, with our hopes and the world's hopes for peace in the balance every day, I do not believe that I should devote an hour or a day of my time to any personal partisan causes or to any duties other than the awesome duties of this office--the Presidency of your country.
Accordingly, I shall not seek, and I will not accept, the nomination of my party for another term as your President.
But let men everywhere know, however, that a strong, a confident, and a vigilant America stands ready tonight to seek an honorable peace--and stands ready tonight to defend an honored cause--whatever the price, whatever the burden, whatever the sacrifice that duty may require.
His address to the nation was much longer than this excerpt and can be found here at the University of Texas/Johnson Library website. This address in my mind goes hand in hand with Cronkite's "Stalemate" speech--Johnson said following Cronkite's speech: "If I've lost Cronkite, I've lost middle America." And he made his decision to not seek re-election.