The selection in March of the Beijing loyalist Carrie Lam as Hong Kong’s next leader is the latest sign that China will continue to tighten its grip on this city. Political divisions will deepen and mistrust of the government will rise.

Ms. Lam, who was picked to be chief executive by an election committee stacked in Beijing’s favor, has long taken a hard-line approach to suppressing dissent. As the former No. 2 official under the unpopular outgoing leader, Leung Chun-ying, she presided over the political reform process that ignited the Umbrella Movement of 2014, in which tens of thousands of Hong Kongers occupied major thoroughfares for three months demanding democratic rights.

With Hong Kong’s autonomy plummeting to a 20-year low, it’s more important than ever for Washington to affirm its commitment to freedom in Hong Kong. The Hong Kong Human Rights and Democracy Act, introduced by a bipartisan group of senators in February, would put the Hong Kong people’s rights at the center of United States policy toward the semiautonomous Chinese territory.

The legislation, an update to a 1992 law governing relations between the United States and Hong Kong, would authorize the president to freeze United States-based assets of individuals who have suppressed freedoms in Hong Kong and deny them entry to America, require the secretary of state to issue an annual report on Hong Kong’s political situation until at least 2023 and guarantee that Hong Kongers who have participated in nonviolent assembly would not be denied American visas on the basis of their arrest.

Our freedoms in Hong Kong have been increasingly squeezed since 2014, when the Chinese leadership in Beijing decided against democratizing the process for selecting our leader, inciting the months of protests.

A renowned legal scholar and former law school dean at Hong Kong University was denied a promotion to a top leadership post at the university because of his pro-democracy positions. Five Hong Kongers working for a bookseller that sold books critical of Beijing were abducted and taken across the border to China, where one was coerced into confessing to crimes on national television. Democratically elected lawmakers in the opposition camp have been facing costly lawsuits filed by the government to disqualify their seats. Democracy activists have been rounded up for leading protests against the government.

Beijing’s fear of separatism and President Xi Jinping’s uncompromising leadership style mean the situation is likely to get worse before it gets better. The Hong Kong Human Rights and Democracy Act would put much-needed pressure on American presidents to stand up to Beijing for its aggression against the people of this territory.

No United States president has visited Hong Kong since Bill Clinton in 1998. The State Department stopped issuing periodic assessments of Hong Kong’s political situation in 2007. Former President Barack Obama showed only tepid support for the Hong Kong democracy movement.

President Trump hasn’t spoken much yet about Hong Kong, but his China policy has been disappointing. He showed some early signs of hope when, as president-elect, he seemed willing to challenge the unjust “One China” policy on Taiwan, but he has since backed off from his tough talk against Beijing.

Congress should do its part to renew White House interest in Hong Kong, sending a message that the United States is concerned about our political freedom. Hong Kong, in spite of all the difficulties it is facing, remains the freest territory under Chinese control. For dissidents in the mainland, Hong Kong’s social movements have long been sources of hope. Safeguarding what has made Hong Kong unique is in Washington’s interest, especially if Americans wish to someday see a free and democratic China.

The Hong Kong Human Rights and Democracy Act — recently introduced in the Senate by Republican Senators Marco Rubio and Tom Cotton, along with Democratic Senator Benjamin Cardin — has received bipartisan backing at this early stage. American conservatives and liberals alike should support the bill and help uphold their shared values of freedom and democracy for this corner of the world.