(NewsNation) — Texas Gov. Greg Abbott cited Chicago’s sanctuary city status as a reason why he sent two buses of migrants there Wednesday night.

Chicago Mayor Lori Lightfoot, while campaigning, promised to keep the city a sanctuary, tweeting in 2019 in part that the city must “make sure every Chicagoan is safe regardless of citizenship status.”

Hundreds of communities, municipalities and counties across the U.S. consider themselves to have sanctuary policies. That includes New York City and Washington, D.C., where migrants have also been bused from Texas, as well as Newark, New Jersey and Los Angeles.

Some states, like California, Illinois, Oregon and Washington have sanctuary policies, too.

According to Lutheran Immigration and Refugee Service, a sanctuary city or state is one with a policy that “discourages local law enforcement from reporting the immigration status of individuals unless it involves investigation of a serious crime.”

Sometimes it’s an unofficial policy, while other times it is written down.

Former Department of Homeland Security adviser Charles Marino said any place that’s designated itself as a sanctuary city could see a migrant bus arrive from Texas.

“It really is disheartening to see what’s been going on with the moving of migrants within the country for political points,” Marino said, although he said the “root cause” of the issue is the Biden administration’s immigration policies that are “failing to secure the Southwest border.”

As some areas have seen more migrants enter the U.S., President Joe Biden has faced criticism from Republicans and Democrats on his border policies.

At the same time, Biden has defended his administration’s actions on immigration, according to a U.S. News report from last year, pointing to seasonal trends in migration, but also blaming the Trump administration. Biden said, according to U.S. News, that Trump “dismantled” the immigration system and diminished the government’s ability to process migrants.

That’s why, The Hill’s Julia Manchester said on “Morning in America,” the politics behind sending migrants to sanctuary cities cannot be ignored.

“This is a Republican governor from a Republican state of Texas, sending these migrants to three democratically-run cities, Washington, D.C., Chicago and New York,” she said. “So there definitely is a political element to this, but it’s an issue that the Biden administration has really been grappling with for quite some time now.”