The Chalmers capital gains and negative gearing reform package will not pass the Australian Senate in its original form by May 27, 2026 — defined as: legislation either failing to reach a final Senate vote, being defeated outright, or passing only with material amendments (grandfathering of existing investment properties broadly extended, CGT discount reduction reduced by more than 10 percentage points from Chalmers' proposal, or implementation timeline delayed beyond 36 months from the bill's original schedule).

The decisive structural constraint is the pre-election Senate composition (Marxist): Coalition retains blocking capacity through July 1, and the question resolves May 27 — squarely within the pre-mandate window. This single fact gives the ‘blocking or material amendment’ outcome substantial structural backing independent of the political dynamics. The Institutionalist framework then provides the second load-bearing mechanism: path dependence from 35 years of coordinated expectation-formation under the existing regime, Olsonian asymmetry in lobby organization, and the 2019 institutional memory embedded in crossbench calculus. The Austrian framework adds critical specificity: the Greens’ dominant strategy under political market marginalism is maximalist holdout, which does not require the Coalition and Greens to coordinate — their opposed preferences converge on the same procedural outcome (failure of the centrist package). The Keynesian framework contributes the weakest marginal confidence (0.42) but confirms that Minsky-unstable property regimes generate well-organized, well-financed opposition that produces amendment pressure regardless of majority logic. All four frameworks predict the reform does not clear in original form; they disagree only on whether the agent of failure is the Coalition (Marxist, Institutionalist) or an uncoordinated two-front veto (Austrian, Keynesian). Since the claim includes ‘or materially amending’ as a success criterion for the Coalition, this disagreement does not affect the directional prediction. Base rate from Australian Senate property reform history: approximately 70% probability of outright defeat or material amendment when facing organized property-sector resistance with a concentrated lobby advantage. Electoral mandate effect, housing affordability salience, and Greens negotiating flexibility create meaningful uncertainty, trimming from the historical base rate — final confidence set at 0.73.