Trump's Arizona trip emphasizes immigration, prompting Democrats to refine their border messaging.

• During a visit to Arizona, Vice President Kamala Harris was painted as a dark picture by Donald Trump of the U.S.-Mexico border.
• During a press conference, Trump falsely stated that Harris' policy views and immigration record were different, and he recounted several alleged crimes committed by undocumented immigrants.
• As Democrats adopt harder lines on their border messages, Trump's visit took place.

On Thursday, former President Donald Trump depicted a grim scenario of the U.S.-Mexico border under the leadership of Vice President Kamala Harris as president.

Hours before Harris was set to receive her party's presidential nomination at the Democratic National Convention, Trump made a visit to Arizona.

During a one-hour press conference, Trump falsely stated that Harris backed open border policies and presented false information on the number of immigrants who entered the U.S. under the Biden-Harris administration.

"Trump claimed that if Harris is given the opportunity, she will permit more than 100 million illegal aliens to enter the country, resulting in an overrun and the loss of the country's identity."

Trump also described several grisly crimes allegedly committed by undocumented immigrants.

The Trump campaign's strategy involves addressing voters' concerns about undocumented immigrants and the Southern border, and assuring them of a response.

Democrats and Harris continue to work on a unified platform for immigration and border security.

At the Democratic National Convention, speakers attempted to balance empathy for immigrants with the public's preference for stricter border control measures.

"On Wednesday night, House Rep. Tom Suozzi, D-N.Y., stated, "The border is broken, and this nation, constructed by immigrants, is a unique and stunning creation.""

A New York House seat was flipped blue by Suozzi, a House freshman who campaigned on a hawkish border platform.

Last year, the number of migrant crossings at the border increased dramatically, causing cities to become overwhelmed. In response, state governments searched for housing options outside of big cities, but local leaders soon discovered that they did not have the necessary infrastructure to accommodate the influx of immigrants.

In the Chicago convention, Democrats accused Trump of pressuring his Republican allies in Congress to tank a Senate border bill earlier this year, which would have allocated more resources to border security.

Sen. Chris Murphy, D-Conn., stated on Wednesday that Trump was responsible for the demise of the bill. This assertion was later echoed by Harris in her acceptance speech.

Trump was accused by Murphy of intentionally sabotaging the border talks that fell apart, as the ongoing migrant crisis served Trump's political goals.

"Trump thrives on hate and division," said Murphy.

Following the Senate's rejection of the border bill, Biden indicated that he would employ his executive authority to accomplish some of its objectives.

In June, Biden issued an executive order to tighten immigration rules, prompting criticism from progressive immigration advocacy organizations.

Biden's decision aimed to convey to voters concerned about the border that he would not hesitate to take strong border measures.

Some of the speeches at the Democratic convention contained a more difficult tone.

""When Donald Trump visits Texas, he stands alongside officers in uniforms just like mine. However, unlike me, he's not there to help us," said Texas county sheriff Javier Salazar Wednesday."

He added, "When the traffickers didn't stop, she put them in jail."

The decline in migrant crossings can be attributed to Biden's executive action, and its effects are already evident on the ground.

In response to the influx of immigrants, Texas Gov. Greg Abbott sent buses full of migrants out of the state to redistribute them.

According to data obtained by NBC News, the Republican governor had stopped sending migrants north on buses by July.