How did the Tet offensive affect Johnson's popularity?

It effectively ended any hope Johnson had of reelection. The Tet offensive was a massive attack, and although the US and ARVN defeated it in fairly short order, and crushed the Vietcong militarily, the damage done to US public opinion at home was massive. The military and the Johnson administration had been telling the public for years that the US was making progress and that there was light at the end of the tunnel. The massive Tet attacks that nearly took the Marine base at Khe Sahn, took the old Imperial capitol city of Hue and took much of Saigon, including, briefly, the US embassy grounds, showed the public that reports of progress were completely false. Walter Cronkite, a very respected new anchor commented that he could see no hope of victory, and upon hearing that pronouncement over their TV news, Johnson is said to have put his head in his hands and muttered "That's it, if I've lost Cronkite, I've lost the American People." Or at least Words to that effect.