What if Joseph Stalin fails to assassinate Leon Trotsky?

From the standpoint of the West, Stalin was mentally ill, probably paranoid schizophrenic. All of those purges, executions, the arranged Ukrainian famine, the Gulag. There was no need for any of this, it simply was a disturbed aberration of his sick personality. From the standpoint of Russia, the perspective is somewhat different. The Russians, rather like the Chinese, believe in centralized government control as a means of stabilizing and controlling society. Almost no price is too high to pay for a stable, centrally controlled government that can direct and control the people, for purposes of military defense and for providing their basic needs. Take the example of Stalin assassinating Trotsky, in 1940, in Mexico. Many in the West would consider this to be a clear example of Stalin's paranoia. An old, isolated, exiled man, 10,000 miles from Moscow, what harm could he possibly do? Well, that's an interesting question. Trotsky's positions on Communism and Fascism in the 1930's are rather difficult to pin down, and his influence, as Lenin's designated successor, was still considerable. On the whole, Trotsky detested both Hitler and Stalin, but, for personal reasons, his attacks on Stalin were probably more systematically intense. He could hardly be described as a stabilizing influence on the Soviet Union, at the time. And, from Stalin's point of view, that was a problem. Let's consider the situation at the start of Operation Barbarossa, the Nazi attack on the Soviet Union, at the end of June, 1941. Let's suppose that Stalin has failed to assassinate Trotsky by this time. Trotsky has been a little more careful, he didn't let the assassin with the icepick in to see him in private in Mexico, as he did in OTL, and he remains in good health. What effects might this have? Well, first of all, it's rather unclear how Trotsky would have responded to the Nazi attack. Responded publicly he would certainly have done, but, how exactly? Would he have applauded it, as a an opportunity for the Stalinists and the Nazis to destroy each other, rather like American conservatives in the U.S.? This is quite possible, actually. And, this would hardly have helped the Soviet Union survive, I suspect. It might have undermined the will of the Russian people to resist their invaders. Another possibility relates to Stalin's desertion of Moscow just after the start of the invasion. Stalin actually fled in fear -- probably of his own people -- to his dacha. He had to be retrieved from there, by his associates in the Politburo. His first question to them, when they arrived at his dacha, was "Have you come to shoot me?" Now, suppose that Trotsky was still alive and active and making public pronouncements at this time. Bear in mind, Trotsky led the Red Army to victory in the Russian Civil War, and was a brilliant military commander. Is it at all possible the Politburo might have wanted Trotsky back, at this time, in the hopes that he might work his military magic once more? Could Trotsky actually have deposed Stalin in July or August, 1941, if he'd been alive to do it? Could Trotsky have effectively led a defense of the Soviet Union against Nazi Germany, at this time? And, would Leon Trotsky have gone on to lead the Soviet Union, after WWII? And, where would that lead us, exactly?