Hillary Clinton is in hot water for suggesting today that a Republican president might 'round up' illegal immigrants and send them back across the border to Mexico in 'boxcars.'

'I just find that not only absurd, but appalling,' she told reporters at the Democratic National Committee's Summer Meeting in Minneapolis.

She did not indicate whom her ire was aimed at and bypassed a reporter who attempted to ask a follow up question about the 'boxcar' theory.

The Republican National Committee subsequently accused her of lobbing a Holocaust slur at its Oval Office candidates.

Allison Moore, national press secretary for the RNC, said in a statement to Daily Mail Online: 'Not 24 hours removed from calling Republicans terrorists, Hillary Clinton reached a new low today hurling Holocaust references at her political opponents.

'Hillary Clinton may be getting desperate over her sinking poll numbers and growing email scandal, but that's no excuse for this kind of inflammatory and extreme rhetoric.'

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Hillary Clinton suggested today that a Republican president might 'round up' illegal immigrants and send them back across the border to Mexico in 'buses' or boxcars.' She did not indicate whom her ire was aimed at and bypassed a reporter who attempted to ask a follow up question about the 'boxcars'

Horror: Boxcars were used by the Nazis to transport Jews across Europe to concentration camps where millions died in mass executions. The use of the term was condemned by Republicans

As the RNC harangued Clinton for invoking Nazi-era imagery of Jews being deported from their countries of residence in boxcar trains, Clinton got some back up from her fellow Democratic presidential candidates, Vermont Senator Bernie Sanders and former Maryland Governor Martin O'Malley.

Sanders, who is Jewish, called Republicans' deportation plans 'racist and the Un-American' and said the country must reject the idea' that we are going to somehow round up millions of people in the dead of the night.'

'It's not what this country is about, and it's not going to happen,' he bellowed to a crowd of Democratic activists.

Asked by DailyMail.com at a press conference if he thought Clinton and Sanders had appropriately described their Republican opponents' stance on deportation measures, O'Malley said, 'Yes.'

I believe that 'in times of apprehension, in times when families are working harder and falling further behind, that any people is vulnerable to the appeals of charlatans and hate mongers who would scapegoat others who are not like us,' O'Malley said.

Several Republican White House candidates, namely Donald Trump, have advocated the mass deportation of the country's illegal immigrants.

He's not said how he plans to achieve that goal, however.

Typically, illegal residents who are escorted out of the country are sent by bus back to Mexico or flown back to their home countries

'I know that there are some on the other side who are seriously advocating to deport 11, 12 million people who are working here,' Clinton told reporters.

And, she said, continuing, 'I find it the height of irony that a party which espouses small government, would want to unleash a massive law enforcement effort, including perhaps, national guard and others, to go and literally pull people out of their homes and their work places, round them up, put them in, I don't know, buses, boxcars, in order to take them across our border.'

Clinton said that is why she supports comprehensive immigration reform that would not only allow illegal residents to remain in the country but would offer them a pathway to U.S. citizenship.

'And i was a deep disappointment to me,' Clinton, a former U.S. senator, said, that when there was a bipartisan agreement in the Senate in 2013, 'the House would not even give it a vote.'

'So I will, I will oppose in every way I can, what I consider to be nothing but a political stunt, and will also raise questions as I am doing today about what the realities of that kind of claim actually are,' Clinton said.

She moved on as another reporter shouted at her about the boxcars.

O'Malley called Trump out explicitly.

'When Donald Trump speaks in those sort of racist ways, about whole groups of immigrants, all of us have a responsibility to push back and to call forward the lessons of history, which teach us, that all of us must stand up and speak out when these sorts of things happen,' he said.

That's because not to speak out is, 'in essence,' he said, to be 'complicit.'

Boxcars: The boxcar (seen in a Canadian National train above) is used to transport almost any kind of freight. It has become grimly associated with the Holocaust through their evil use by the Nazis.

In her speech before Democratic activists gathered in the Hilton Minneapolis ballroom immediately prior, she ripped Donald Trump for trying to take away birthright citizenship for the children of illegal immigrants, however

In her speech before Democratic activists gathered in the Hilton Minneapolis ballroom earlier that afternoon, Clinton had ripped Trump for trying to take away birthright citizenship for the children of illegal immigrants.

'Look, you hear Mr. Trump say hateful things about immigrants, even about their babies,' she said a few minutes later.

How many others disagree with him or support a real path to citizenship, she asked, or 'draw the line' at repealing the 14th amendment?

'Today the party of [Abraham] Lincoln has become the party of Trump.'

Bringing her long speech, which went over the allotted time, back to the topic of immigration a little later, Clinton fired in the direction of Jeb Bush while talking about women's issues and said, 'We're not going to stay quiet while [Republicans] demonize women, whether they're Latino, Asian or anything else.'

She was referring to Bush's remarks on 'anchor babies' - a controversy that the ex-Florida governor further fueled this week when he claimed he wasn't talking ill of Hispanics, whom he feels a kindred spirit with as the husband of a Mexican native.

Instead, Bush said he was thinking of Asians.

In her remarks, Democratic National Committee Chairwoman Debbie Wasserman Schultz also singled out Trump and Bush, as well as Florida Senator Marco Rubio.

'Republicans rushed to follow [Trump's] lead' on eliminating birthright citizenship, even Rubio, she claimed.

Rubio is the son of Cuban immigrants, who were living in the country legally when he was born, and an author of the Senate's comprehensive immigration reform bill from the previous congressional session.

He and Bush share a home state with Wasserman Schultz, making them easy targets for her criticisms.

Bush, she said, like Trump, used a 'vulgar and disgusting term' to describe children born to illegal immigrants in America.