It is not clear whether Mr. O’Rourke would be able to get Congress to agree to a sweeping rewrite of the country’s immigration and naturalization laws, but he pledged to use his first 100 days in office to push for a path to citizenship for undocumented immigrants, increase visas and make the naturalization process easier for the nearly nine million immigrants who are currently eligible for citizenship.

At the same time, Mr. O’Rourke argued for bolstered security and infrastructure at parts of the border where trade and travel occur. But he vowed to suspend construction of and cancel funding for Mr. Trump’s proposed border wall. Mr. O’Rourke has often pointed to El Paso, which borders Mexico and is one of the safer cities of its size in the United States, to argue that a wall is unnecessary.

And while he called for increased accountability for ICE, he did not suggest abolishing the agency. He also said the country should address visa overstays through better tracking systems to ensure “we remain a nation of laws.”

Mr. O’Rourke’s plan seeks a $5 billion investment in Latin America aimed at “reversing the instability that drives forced migration,” which would be mostly funneled through nongovernmental organizations, community groups and public-private partnerships. The plan also calls for the formation of a regional alliance “dedicated to creating stability and economic prosperity.”

Ali Noorani, the executive director of the National Immigration Forum, an immigration advocacy organization, said Mr. O’Rourke’s plan “seems to cover all the bases,” but he was particularly interested in its focus on border security and Latin America.

“The assumption is the Democrats are against the idea of immigration enforcement,” so it was important that Mr. O’Rourke clearly stated otherwise, Mr. Noorani said. “Democrats need to put forward plans that look beyond the Democratic base,” he said.

“To have foreign policy as a component of an immigration policy plan is a productive step forward,” Mr. Noorani added. “Americans understand that immigration represents a set of complicated problems and they are looking for complicated solutions.”