President Biden had big ambitions for remaking America’s immigration system.

He said he would secure the border. He promised to make the asylum system work. He vowed to protect Dreamers. On the first day of his presidency, he proposed legislation to create a path to citizenship for millions of undocumented immigrants.

Most importantly, he said he would bridge the partisan divide that has long prevented any overhaul of an archaic immigration system that his aides often describe as a “decades-old jalopy” in desperate need of upgrades.

But for four years, most of those goals were stymied by the need to confront a worldwide surge of displaced people fleeing their homes and a determined Republican opposition that seized on scenes of a chaotic border to block action and damage the president politically.

The president’s early efforts to reverse some of his predecessor’s harsh policies won praise from liberals but soon left him open to attacks by conservatives who said he had all but invited migrants to flock to the border. As the issue flared, and even Democrats complained, Mr. Biden embraced tougher measures and was sharply criticized by immigration advocates.

In the end, Mr. Biden’s legacy on immigration was largely limited to his eventual success in reducing illegal border crossings to their lowest levels in more than four years. At the peak of the surge at the end of 2023, a quarter-million migrants crossed into the United States in a single month. As voters elect the next president, that number has dropped to around 50,000 — lower than parts of his predecessor’s tenure.

But the immigration system Mr. Biden pledged to fix remains fundamentally broken, and some of his actions at the border moved the problem deeper into the country.