The Republican governors of Texas, Florida and Arizona have escalated their partisan tactic of sending migrants to Democratic strongholds without advance warning, including to the home of Vice President Kamala Harris.

On Thursday, Texas Governor Greg Abbott sent two busloads of migrants to the Naval Observatory in Washington D.C., not far from the official residence of Vice President Harris.

It was the latest example of the Texas governor's five-month-old operation to to taunt leaders of immigrant-friendly sanctuary cities and stoke opposition to Biden administration border policies. Since April, he has bused 7,900 migrants to the capital, as well as 2,200 to New York and 300 to Chicago.

"The Biden-Harris administration continues ignoring and denying the historic crisis at our southern border, which has endangered and overwhelmed Texas communities for almost two years," said Abbott, who is facing reelection.

Volunteers who were awaiting the arrival of the migrants at another location said they had no warning. President Joe Biden, who was at an event hosted by the Congressional Hispanic Caucus Institute, accused Republicans of "playing politics with human beings, using them as props."

Martha's Vineyard locals step up

On the same day, some 50 migrants were flown by Florida Governor Ron DeSantis to Martha's Vineyard, an exclusive summer holiday island in Massachusetts.

One Venezuelan migrant who identified himself as Luis, 27, told Reuters news agency that he and nine relatives were promised a flight to Massachusetts, along with shelter, support for 90 days, help with work permits and English lessons. He said they were surprised when their flight landed on an island.

"We are scared," he said, adding he and others felt they were lied to. "I hope they give us help."

Residents of the summer retreat stopped by to offer cash donations, legal advice and children's toys. A makeshift shelter was set up in the local Episcopal church.

"It's a stunt to make political points and not caring about who gets hurt," said Mike Savoy, a nurse at Martha's Vineyard Regional High School.

Calls for investigation

California's Democratic Governor Gavin Newsom has called for the Department of Justice (DOJ) to investigate what he called "inhumane efforts to use kids as political pawns."

"What Ron DeSantis and Greg Abbott are doing isn't clever, it's cruel," he said on Twitter.

At an official event on Thursday, DeSantis said he helped the migrants "go to greener pastures."

His Democratic challenger at the upcoming gubernatorial election, Charlie Crist, accused the Florida governor of spending $12 million (€12 million) "to score political points and feed red meat to his base in his thinly veiled attempt to run for president."