The Senior Partner's Split

Five perfectly rational partners at a fund, strictly ranked by seniority, must divide a $100$-unit bonus pool. The most senior partner proposes an allocation of whole units; then all five (including the proposer) vote. If at least half the votes favor it, the split is final. If not, the proposer is expelled from the firm and the next most senior partner makes the next proposal under the same rule. Every partner's priorities, in order: stay at the firm, then maximize units received, then (all else equal) prefer seeing rivals expelled. What allocation does the most senior partner propose, and does it pass?