The recent Senate elections in the Philippines delivered an unexpected result, sparking concerns among those closely following the country’s political landscape. Several allies of former President Rodrigo Duterte, whose administration leaned toward China to strengthen ties, secured key seats in the upper chamber of Congress.

While President Ferdinand “Bongbong” Marcos Jr. has steered the Philippines back toward a stronger security partnership with the United States since 2022, the resurgence of Duterte’s political bloc signals potential turbulence ahead.

The Philippines has emerged as a cornerstone for the U.S. Indo-Pacific strategy. Increasing defense cooperation, expanded access for U.S. forces under the Enhanced Defense Cooperation Agreement (EDCA), and joint military exercises have solidified Manila as a crucial ally in countering China’s aggression in the South China Sea.

The U.S.-Philippines Bilateral Defense Guidelines, established in May 2023, reaffirm that an armed attack on either country’s forces in the Pacific, including over disputed territory in the South China Sea, would trigger mutual defense commitments under the 1951 Mutual Defense Treaty.

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The Guidelines also emphasize cooperation between various military groups, modernization of defense capabilities, and joint maritime patrols to counter threats in the region.

With nine Philippine military bases now accessible to U.S. forces, including four additional bases identified in 2023, the agreement enhances deterrence against Chinese aggression and provides strategic positioning near Taiwan.

But this newfound alignment could be undercut from within due to the Senate election results.

Vice President Sara Duterte, the former president’s daughter, is facing an impeachment trial in the Senate set for July. If convicted, she would be removed from office and permanently barred from running for any future political position, including the 2028 presidential election.

The Senate election results have given Duterte a boost, however, with five of the 12 newly elected senators being her allies. That includes Imee Marcos, the sister of President Marcos Jr. The Vice President needs at least nine senators to vote for her acquittal to remain in office.

If Duterte’s allies gain more influence and she survives the impeachment trials, the Philippines could once again start to shift its foreign policy back towards China, reducing U.S. leverage in the region and complicating Indo-Pacific security efforts.

Beijing has historically capitalized on political division to expand its influence, particularly through economic investments and infrastructure projects. If Duterte’s faction regains power, China will look to strengthen its foothold in the Philippines, potentially undermining U.S. efforts to maintain a free and open Indo-Pacific.

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During former President Duterte’s term in office, territorial disputes in the South China Sea were downplayed, as Duterte opted for economic cooperation with Beijing rather than enforcing the 2016 international tribunal ruling that invalidated China’s expansive maritime claims.

Economic dependence on China also deepened as Duterte secured billions in investment pledges, including infrastructure projects under Beijing’s Belt and Road Initiative. However, many of these projects failed to materialize, leaving the Philippines economically vulnerable while China continued its military expansion in contested waters.

President Duterte’s approach weakened Manila’s alignment with the U.S., creating uncertainty about the Mutual Defense Treaty and joint military operations.

If Sara Duterte survives the Senate proceedings and consolidates power, the Duterte dynasty could stage a comeback, setting the stage for a 2028 presidential bid that might shift Manila’s foreign policy back toward Beijing.

For Washington, the stakes couldn’t be higher. The Philippines is a critical ally in the Indo-Pacific strategy, and another Duterte family presidency could jeopardize military agreements, reduce U.S. access to key bases, and complicate efforts to counter Chinese aggression.

As the 2028 election approaches, policymakers in Washington must closely monitor the shifting political tides in Manila—because if the Dutertes return to power, the balance of power in the South China Sea could tilt in Beijing’s favor.