Facing setbacks, Vladimir Putin makes his biggest gamble yet in Ukraine

Well, just like in WW2, the communists called for "patriots" to fight for "Mother Russia" (and not the Communist Party), I don't think that Putin is "positioning" this as a "fight for him". He is trying to paint this as a "the West is trying to 'corner' Russia" situation. However, your doubt is well placed. Modern technology makes a lot more information available to the average Russian. Many either disagree with or don't understand the war. Popular support, other than in the border provinces - where people have been told that Ukrainians want to invade their homes - is lagging. And the idea of going off to a war where the news of corpses being brought back is slowly filtering to the population, is not exactly enticing. Many "draft eligible" men have been trying to leave the country... which is why Putin is prohibiting people from leaving. So - yes - he may in fact find it hard to find 300 thousand men who will willingly sign up. As a matter of fact, he can't. That's the reason for the draft. Now we will see whether he can actually carry out the draft and meet the target he set. Putin is fighting for his political life. He realizes he is operating within a system that can articulate a regime change under the guise of a military/security operation that may have him "arrested" or "dying trying to escape". It depends on whether the people he has placed in key positions will continue to support him. And they'll do that as long as they think they can hold on to their positions of privilege. If things get to the point where they lose confidence, all bets are off. Putin knows this, so he's playing his cards accordingly. We shall see how this plays out.