Biden is not going to be able to sell US Involvement in this regional conflict with a bad guy where we have no vital national security interest indefinitely. Western Europe, who does have a vital national security interest in it and does not care one wit whether Putin ultimately annexes those Eastern Ukraine provinces, is already itching to get it over with to repair their faltering economies and get back to importing cheap Russian gas. Bottom line, they will get more vocal about negotiating an end to the conflict and the US public will shortly thereafter get more vocal about the billions we are spending there. IMHO, politically, Biden has another 6-9 months of playing with this thing before he has to fold his cards and give in to Western European pressure to push Zelensky to the negotiation table.