This is an epic defeat for the PT and one more in a long series of strategic maneuvers by the PMDB, which has been the soft center of Brazilian politics since the tail end of Brazil’s long military dictatorship (1964-85). The PMDB is a deal-making, non-ideological party. For a generation, it has served as the glue of fractious coalitions in Brazil’s multiparty system, where over 20 parties are represented in Congress. The PMDB is quick to adhere to any governing coalition — for the right price — but when it deserts, the coalition falls apart. Breaking up is hard to do for ideological parties: once driven from power, they lose control over favored initiatives and are left to recuperate in the political wilderness. But it is easy for the PMDB, which coalesces around the next unlikely collection of interest groups and oozes onward.

Economist Albert O Hirschman famously analyzed the decline of membership organizations in terms of exit, voice and loyalty. Dissatisfied members choose to exit or to voice their discontent. That choice is shaped, in part, by loyalty: in organizations characterized by a high degree of loyalty, members are less likely to exit. Hirschman’s analysis is useful for any consideration of the low-loyalty context of Brazilian political coalitions. But another set of terms may be more illuminating: dissolution, compromise and cover-up.

When coalitions dissolve, survivors seek compromise with former opponents. Members of the new coalition then join forces to cover up their role in whatever led to the dissolution of the old coalition. Rousseff’s PT is unlikely to survive the current dissolution in its current form. The PT’s 13 years of power depended on a rare convergence of interests of organized labor, big business and social movements—a convergence sustained by the economic growth Brazil enjoyed during a period of rising commodity prices, successful economic reforms and implementation of redistributive social spending. Plunging commodity prices, along with Rousseff’s own unsuccessful policies, have ended this convergence for the foreseeable future. The PT will have to pick up the pieces.

The PMDB, in contrast, always seems to get the comfy sofa in the musical-chairs game of Brazilian politics. For 13 years it backed the PT. With the PT fallen on hard times, the PMDB slides to the opposition. And the opposition, which only a few months ago slammed the PMDB for its role in government corruption, now depends on that party to hold its own emerging coalition together.

Rousseff is ostensibly being impeached for budgetary manipulation that enabled her to conceal deficits during her reelection campaign in 2014, but this common practice would pass unnoticed in better times. More seriously, the PT has apparently presided over an extensive system of kickbacks from government contractors to elected officials. Rousseff herself has not been directly implicated in this scheme. High-ranking PMDB officials, in contrast, are under investigation, as are politicians from most Brazilian parties. Bringing the PMDB into power to clean up Brazilian politics is akin to cleaning the floor with a dirty mop.

Should Michel Temer rise to the presidency, the only way for the current opposition to hold a coalition together will be to stifle or divert the ongoing investigation. The PT’s coalition has already dissolved. The PMDB and historic opponents of Rousseff’s PT are now arranging the terms of their compromise. Get ready for the cover-up.

Bryan McCann is a professor of Latin American History at Georgetown University.