Martin O’Malley is mired at the bottom of the polls and struggling to raise money for his presidential bid, but Vermont Sen. Bernie Sanders' campaign is circulating an internal document to its staff and supporters tearing down the former Maryland governor’s immigration plan.

“While Governor O’Malley’s immigration platform is more detailed and progressive [than] Clinton, there are many immigration policy areas that it does not address,” reads the document, which goes on to outline how Sanders is more substantive on immigration policy than O’Malley on about a dozen issues including “enforcement, detention and humanitarian relief.”

A Sanders spokesman, Michael Briggs, denied the document constituted opposition research on a candidate still striving to gain any traction in the race. “We don’t see any reason to do opposition research on Gov. O’Malley,” he said, describing the memo as an “internal, matter-of-fact document sent to our staff and supporters comparing plans so people can have a better understanding of Bernie's proposals.”

The compare-and-contrast makes no mention of any of Hillary Clinton’s immigration reform proposals.

Sanders, who enjoys high popularity in states like Iowa and New Hampshire, has had less success attracting Latino voters. The campaign reached out to the Hispanic community in Las Vegas earlier this month, putting on a large rally featuring a mariachi band and Spanish language posters. But even there, the majority of the audience that came out to hear Sanders speak was white.

Since launching his campaign last June, O’Malley, a longtime supporter of immigrants’ rights, has focused on Latino voters and he recently blasted Clinton for using the loaded term “illegal immigrants” at a campaign stop. In a Facebook chat Tuesday, Clinton admitted “illegal” was a “poor choice of words” and said she would not use the term again.

But O’Malley is languishing in the polls -- he received 4 percent compared to 42 percent for Sanders and 51 percent for Clinton in a Quinnipiac poll of Iowa voters released Wednesday. A day earlier, his campaign announced it would accept public financing -- a last-ditch move that will limit his primary spending to $48 million.

Still, the Sanders campaign appears to be trying to make inroads by challenging his immigration reform proposals.

“Unlike the O’Malley platform, the Sanders platform speaks to providing deferred action to undocumented immigrants engaged in labor disputes, eliminating the ‘significant misdemeanor’ bar in enforcement, and providing discretion for immigrants with non-immigration convictions, such as identity theft, driving without a license felonies, and survival crimes,” the internal document reads. It says that Sanders, unlike O'Malley, "outlines what a roadmap to citizenship should encompass," including expedited citizenship, federal financial aid and immediate service in the armed forces for DREAMers.

And it points out that “while Governor O’Malley wants to limit detention and close inhumane detention facilities, Senator Sanders goes even further, additionally calling for the closure of all for-profit detention facilities.”

The Sanders plan, the document claims, is less elitist than O’Malley’s proposals. “Unlike the O’Malley platform, the Sanders platform does not afford special treatment to “high-skilled” workers that big corporations demand, and instead includes workers of all backgrounds.” 

When asked for comment, O'Malley spokeswoman Lis Smith ripped Sanders, attacking his campaign's motives for assembling the document.

"They only feel the need to whitewash Sanders' nativist and offensive immigration statements by comparing their immigration 'plan' to Martin O'Malley's? It will take a lot more than a bad copy and paste job for them to catch up with someone who has actually been a leader on this issues," she said.