Obama's Homeland Security secretary says 2020 Democrats' immigration proposals are practically 'open borders'

William B. Plowman/NBC/NBC NewsWire via Getty Images)

Former DHS Secretary Jeh Johnson.

• Democratic presidential candidates' embrace of proposals like decriminalizing illegal border crossings is "tantamount to declaring publicly that we have open borders," according to Jeh Johnson, who ran the Department of Homeland Security under President Barack Obama.
• Former Housing and Urban Development Secretary Julián Castro challenged his fellow Democrats on the debate stage last week to support repealing Section 1325, which makes it illegal for aliens to enter the US.
• Many of the candidates on stage agreed with Castro.
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Democratic presidential candidate and former Housing and Urban Development Secretary Julián Castro challenged fellow candidates to support decriminalizing illegal border crossings at the first primary debates, a stance that a top Homeland Security official in the Obama administration called practically an embrace of "open borders."

Jeh Johnson, who served as secretary of the Department of Homeland Security during President Barack Obama's second term, told the Washington Post that some 2020 Democrats are pushing border security reforms that may be ineffective and are outside the immigration polices that most Americans want.

Read more: Julián Castro is running for president in 2020. Here's everything we know about the candidate and how he stacks up against the competition.

"That is tantamount to declaring publicly that we have open borders," Johnson said. "That is unworkable, unwise and does not have the support of a majority of American people or the Congress, and if we had such a policy, instead of 100,000 apprehensions a month, it will be multiples of that."

At the first primary debate in Miami last Thursday, Castro demanded his fellow Democratic candidates embrace the repeal of Section 1325, which makes it a crime for aliens to improperly come across the border.

Read more: Half of Democratic primary voters support decriminalizing illegal entry into the US

When former Rep. Beto O'Rourke did not embrace Castro's challenge, the Texas rivals got into a spat that created the one of the more viral moments of the evening.

"I think that you should do your homework on this issue," Castro told O'Rourke. "If you did your homework on this issue, you would know that we should repeal this section."

Read more: Congress sends massive border-funding bill to Trump's desk after Nancy Pelosi caves under pressure

Sen. Amy Klobuchar of Minnesota also tried to reel in the conversation by talking about going after smugglers and human traffickers, whose border crossings she would not want to decriminalize.

"But I do think you want to make sure that you have provisions in place that allow you to go after traffickers and allow you to go after people who are violating the law," she said.