Three weeks of expanding Ukrainian occupation of Russian territory should make it very clear that Russia simply lacks the troops to protect its own homeland. If Russia still had massive reserves, there would be no rational reason to allow this humiliation instead of signaling strength.
Russian losses have been massive, with hundreds of thousands of casualties. And it's showing. They are incapable of continuing to advance inside Ukraine and protecting their own borders at the same time.
The only way for Russia to win is to influence Western elections in its favor in order to prevent further aid. Unfortunately, that might work.