A supporter of the Cambodian People’s Party holds a portrait of Prime Minister Hun Sen in Phnom Penh, Cambodia, on Friday. (Mark Remissa/EPA-EFE)

Sam Rainsy is the former leader of the Cambodia National Rescue Party and the president of the Cambodia National Rescue Movement.

This week, the U.S. House of Representatives passed the bipartisan Cambodia Democracy Act to impose sanctions on Cambodian government officials for directly undermining democracy. The House’s timing is no coincidence: On Sunday, Cambodia’s brutal prime minister, Hun Sen, will seek to further entrench his three-decade hold on power through a sham election.

As an exiled politician from Cambodia, I’ve been watching this unfold with alarm. Hun Sen, a former Khmer Rouge commander, has grown more and more authoritarian in recent years. Most recently, he forcibly dissolved his only viable political opponent: the Cambodia National Rescue Party (CNRP), which I used to lead. Now that he’s running virtually unopposed this Sunday, our national election is rendered meaningless.

For months now, democracy in Cambodia has been unraveling. Those of us who know Cambodia’s history have grown terrified watching political developments that could set the stage for a return to our recent past, when the Khmer Rouge’s brutal reign left 1.7 million Cambodians dead. Hun Sen, who was part of that deadly reign, has grown increasingly desperate to consolidate his power.

While our country’s constitution defines Cambodia as a democracy, in reality Cambodia is an oppressive one-party state. Over the past nine months, in addition to disbanding his only political opposition, Hun Sen presided over the arrests of protesters and cracked down on all independent media.

Make no mistake: When he dissolved the CNRP, Hun Sen did not eliminate a fringe opposition group. In the June 2017 local elections, the CNRP won more than 40 percent of the popular vote. Hun Sen used our own government systems — the parliament and the judiciary — to dissolve our party. He also threatened and exiled me, and beat and jailed my friends and colleagues.

Hun Sen launched these egregious attacks on democracy and human rights with one goal in mind: to run unopposed in national elections on Sunday and solidify his power for years to come. Sunday’s election will be meaningless without the CNRP’s participation as the only viable opposition party in Cambodia — and without international oversight to ensure fair play.

Hun Sen is guaranteed to win the election by the kind of margin seen only in totalitarian states. That is why I call on fellow Cambodians to show Hun Sen that his time is up by boycotting this “fake” election, and on Western powers to pressure him with targeted sanctions like those the House just passed.

If the U.S. and the international community accept Hun Sen’s declaration of victory after this sham election, they will legitimize his rule and encourage other authoritarian leaders in Southeast Asia and across the globe. Turning a blind eye to Hun Sen’s rigged vote would set back the positive trend of democratization witnessed across the region, from Malaysia to East Timor.

By striking back against Hun Sen with political and economic pressure, the U.S. and the international community can deliver a forceful rebuke of authoritarianism and send a warning to leaders who might be tempted to follow Hun Sen’s path. While the House’s bill is an important first step, we must ensure the Cambodia Democracy Act passes through the legislature and into law.

Governments that accept these election results will be complicit in moving Cambodia closer to the horrors of its past and fueling the rise of authoritarianism across the globe. That’s why all countries committed to democracy and human rights should recall their ambassadors to Cambodia; introduce sanctions targeting Hun Sen, his family and close collaborators; and revoke trade privileges for Cambodian businesses with ties to the regime.

Hun Sen is fearsome. But our international opposition movement is strong, and the world has helped topple dictators before. If we band together now, we can rescue Cambodia from dictatorship.