Nearly three years after U.S. regulators first proposed sweeping changes to bank capital requirements, the Basel III Endgame rule remains unfinished. Federal Reserve Vice Chair for Supervision Michelle Bowman indicated in late 2025 that a revised proposal could emerge by early 2026, but the timeline has shifted repeatedly since the original July 2023 notice of proposed rulemaking.1 For middle market dealmakers, the regulatory ambiguity has become a market reality in itself — one that continues to reshape lending relationships, deal structures, and competitive dynamics across the capital stack.
The original proposal estimated aggregate capital increases of roughly 16 percent for the largest U.S. banks, with globally systemically important banks facing increases as high as 21 percent.2 While the re-proposal is widely expected to moderate those figures — Federal Reserve officials have signaled a move toward “capital neutrality” — the behavioral effects among bank lenders have already taken root. S&P Global data shows that bank participation in middle market leveraged lending has declined steadily since 2023, with direct lenders now financing approximately 90 percent of buyout transactions below $500 million in enterprise value.
The regulatory overhang, in other words, has accelerated a structural shift that was already underway. And the implications extend well beyond the banks themselves.
How Regulatory Uncertainty Becomes Lending Retreat
Bank credit committees do not wait for final rules to adjust behavior. The mere prospect of higher risk-weighted asset charges on leveraged lending portfolios has prompted a measurable pullback in commitment sizes, hold levels, and appetite for sponsor-backed transactions. Several large regional banks have exited middle market leveraged lending entirely since 2024, redirecting balance sheet capacity toward investment-grade relationships and fee-based advisory mandates.
PwC’s analysis of the Endgame proposal notes that the capital impact falls disproportionately on trading activities, but lending portfolios face meaningful effects as well — particularly for exposures that carry higher risk weights under the standardized approach.3 Middle market leveraged loans, which typically involve higher leverage multiples and less liquid secondary markets, sit squarely in the category of exposures that become more capital-intensive under the proposed framework.
The practical result is a widening gap between what bank lenders can offer and what sponsors require. Hold sizes that once reached $75 million to $100 million at individual banks have contracted to $30 million to $50 million in many cases, forcing arrangers to assemble larger club groups or, increasingly, to cede the mandate to direct lenders who face no comparable capital constraints.
Private Credit as the Structural Beneficiary
The displacement of bank capital from middle market lending has been the single largest tailwind for private credit growth over the past decade, and Basel III Endgame — whether finalized or not — extends that trajectory. Lord Abbett estimates that roughly 200,000 U.S. companies with annual revenues between $10 million and $1 billion represent approximately one-third of private sector GDP, a vast addressable market increasingly served by non-bank lenders.4
Direct lenders have moved aggressively to fill the void. Platforms that historically focused on unitranche facilities for sponsored transactions have expanded into asset-based lending, equipment finance, and specialty verticals that banks once dominated. The competitive advantage is not merely regulatory — private credit funds offer speed to close, documentation flexibility, and willingness to hold entire commitments that banks structurally cannot match under tighter capital regimes.
Morgan Stanley projects private credit assets under management will grow from approximately $1.7 trillion in 2024 to $2.8 trillion by 2028, with the bank-to-private-credit migration representing a significant share of incremental flows.5 For middle market borrowers, the transition means fewer banking relationships and greater dependence on a concentrated set of alternative lenders — a dynamic that carries its own set of risks.
The Bank Response: Non-Regulated Affiliates and Hybrid Structures
Banks have not conceded the middle market entirely. Several of the largest institutions have responded to regulatory pressure by establishing or expanding non-regulated affiliates — BDCs, separately managed accounts, and co-lending vehicles that sit outside the bank holding company’s consolidated capital requirements. The Wells Fargo-Centerbridge and Apollo-Citi partnerships represent large-cap templates, but analogous structures are proliferating in the middle market as well.
These hybrid models allow banks to maintain client relationships and origination capabilities while shifting funded exposure to capital-unconstrained partners. For sponsors and borrowers, the structures offer the comfort of a bank relationship with the execution certainty of private credit. For the banks, they preserve fee income and relationship primacy without consuming scarce regulatory capital.
Legal complexity is considerable. Structuring bank-affiliated lending vehicles requires careful navigation of affiliate transaction rules, Volcker Rule considerations, and inter-company risk transfer regulations. Law firms specializing in financial services regulatory work report that bank-private credit partnership mandates have become one of the fastest-growing practice areas since 2024.
Implications for the Broader Ecosystem
The regulatory-driven shift in lending capacity has cascading effects across the middle market ecosystem. Investment bankers report that financing certainty has become a more significant factor in sell-side processes, with buyers increasingly favoring private credit commitments over bank-arranged syndications that carry execution risk. Turnaround advisors note that the reduced bank presence in leveraged lending has also diminished the availability of bank workout expertise — a gap that could prove consequential if default rates rise from current levels near 3 percent toward the 5 percent stress scenario that KBRA has modeled.6
For legal advisors, the evolution creates both complexity and opportunity. Refinancings from bank facilities to private credit require documentation overhauls, as private credit agreements differ materially from bank credit agreements in areas including covenant structures, amendment mechanics, and lender consent rights. A managing partner at a middle market-focused law firm estimates that bank-to-private-credit refinancing mandates now account for 20 to 25 percent of the firm’s lending practice revenue, up from less than 5 percent three years ago.
Conclusion
Basel III Endgame may ultimately arrive in a form far less punitive than initially proposed. The political environment has shifted, regulatory leadership has turned over, and the re-proposal is expected to reflect a more calibrated approach to capital requirements. But the market has already priced in the direction of travel. Banks are structurally less willing to commit capital to leveraged middle market lending, and the infrastructure that private credit has built to absorb that displacement is unlikely to reverse even if final capital requirements prove modest.
For middle market participants — sponsors, borrowers, advisors, and lenders alike — the practical question is not whether Basel III Endgame will pass, but how to navigate a market in which the regulatory overhang has permanently altered the lending landscape. The banks that adapt through hybrid structures and non-regulated affiliates will retain relevance. Those that wait for regulatory clarity before acting may find the market has moved on without them.
Footnotes
- Bloomberg Professional Services, “Fed Remarks Point to Capital-Neutral Basel III Endgame in 2026,” September 2025.
- PwC Financial Services, “Basel III Endgame: The Next Generation of Risk-Weighted Assets,” 2024.
- PwC Our Take, “Basel III Endgame: Complete Regulatory Capital Overhaul,” 2025.
- Lord Abbett, “Prospects for Private Credit in 2026,” 2025.
- Morgan Stanley, Private Credit Market Outlook, 2024.
- KBRA, Private Credit Default Rate Projections, 2025.
