There’s a poorly constructed window in a tall building waiting for him
If they want to stop him, they will probably use his weak point: fundraising. He is trying to get 26 million rubles (about $290,000) and now has about 1.7 million. The maximum amount to pay is 2.4 million rubles. They will pay a larger amount from some account and say that it is from abroad or similar and then explain that Nadezhdin is a “foreign agent”.
Nadezhdin’s staff has probably thought about this and done something to check the payment and send them back or send unclear payments to the Russian treasury or similar.
Note that Nadezhdin says that on day 1 after winning the election he will stop the war and send all soldiers home from Ukraine. This is what the Kremlin has difficulty with. The Putin gang is planning a partial mobilization before the election to gain support, and after the election (in April) a total mobilization to make major attacks in Ukraine and in other countries (e.g. Moldova?) The next few months will be interesting.