BALTIMORE – For the second night in a row, Democratic presidential candidates used a nationally televised debate to call out President Donald Trump for his tweets critical of conditions in Baltimore and of elected leaders' handling of the city's problems.

Several candidates invoked Trump's Baltimore-related tweets, and former U.S. Housing and Urban Development Secretary Julian Castro said: "First of all, the president is a racist. And that was just one more example of it."

New Jersey Sen. Cory Booker cited the tweets in his opening statement.

"Last week, the president of the United States attacked an American city, calling it a disgusting, rat-infested … mess," Booker said on the second night of the second round of Democratic debates in Detroit.

"Donald Trump, from Charleston to Baltimore to even the border, is using the tired old language of demagogues, of fearmongers, of racists, to try to divide our country against itself," Booker said. "We know who Donald Trump is, but in this election the question is who are we as a people?"

Booker's remarks were briefly interrupted by chants of protesters seeking the firing of a New York City police officer involved in a fatal confrontation.

Later, CNN anchor Don Lemon posed a question about Baltimore Mayor Bernard C. "Jack" Young calling in to CNN on Monday with a message for Trump. "If he wants to make America great again, put the money in cities that need it most," Young said at the time.

"What would you do for Baltimore and other cities that need help?" Lemon asked after quoting Young.

That was when Castro called the president a racist. Castro also said he would invest in providing more educational opportunities and would "invest in housing that is affordable."

Castro said people shouldn't have to leave West Baltimore and other struggling areas "if you want to reach your American dream."

Trump continued to tweet Wednesday about Cummings and Baltimore. He has called the district of Rep. Elijah Cummings, a Baltimore Democrat, "disgusting, rat and rodent infested" and told reporters that billions of dollars in federal aid to Baltimore has been "wasted" and "stolen."

On Wednesday, Trump tweeted an old video of Cummings at a congressional hearing calling a section of Baltimore "a drug-infested area." The president said he has been criticized for using such a term and suggested Cummings should be treated the same.

Many of the Democratic presidential contenders had tweeted their defense of the congressman and the city before the debates Tuesday and Wednesday nights.

On Tuesday night, Minnesota Sen. Amy Klobuchar referenced Trump's tweets.

"Little kids literally woke up this weekend, turned on the TV, and saw their president calling their city, the town of Baltimore, nothing more than a home for rats," Klobuchar said.