When Mitt Romney holds a fundraiser with Donald Trump later today in Las Vegas, he’ll try his best to smile as he rakes in $2 million with the help of the real estate heir, casino mogul, television star, and purveyor of racially-charged conspiracy theories about President Obama’s birthplace.

But there is one group that can hardly contain its joy: Democrats, who see Romney’s forced embrace of the reality TV star as easy attack fodder.

The Obama campaign released a video early Tuesday showing some of Trump’s more outlandish comments set to circus music. The core of the Democrats’ attack is to raise questions about Romney’s character, contrasting his silence on Trump’s birther charges to John McCain’s rebuke to extremists in his party during the 2008 campaign.

The campaign has branded Trump “the birther-in-chief,” and Democrats have flooded reporters’ inboxes with clip after clip about Trump’s wild accusations.

But beyond simply mocking Romney and Trump, Democrats see the relationship as supporting a character attack on the presumptive Republican nominee.

“He is once again failing the moral leadership test that he has already failed so many times — he refused to condemn Rush Limbaugh's attacks on Sandra Fluke; he refused to condemn the Joe Ricketts plan to 'Defeat Barack Obama'; and, he counts Joe Arpaio, the 'birther sheriff', as an endorser,” said DNC Press Secretary Melanie Roussell. “Mitt Romney has shown time and again that he won't stand up for what's right — instead he'll stand with Donald Trump and his conspiracy theories.”

Romney has already come to Sin City once before to meet the “Apprentice” star, for an awkward February endorsement that featured Trump apparently refusing to relinquish the candidate’s hand in an extended grin-and-grip. This time, the pro-labor Super PAC Workers’ Voice will have members outside of the Trump event bearing "I like firing people" and "you're fired" signs — tying Romney’s gaffe to Trump’s mantra, an official at the group said.

And Republicans are struggling to understand Romney’s continued association with Trump, who they fear hurts Romney more than he helps, especially among independents.

“I do not understand the cost benefit here,” conservative columnist George Will said of Romney on ABC's This Week Sunday. “The costs are clear. The benefit — what voter is going to vote for him because he is seen with Donald Trump? The cost of appearing with this bloviating ignoramus is obvious, it seems to me. Donald Trump is redundant evidence that if your net worth is high enough, your IQ can be very low and you can still intrude into American politics.”

One Republican operative questioned the needs to bring Trump out onto the trail even to raise money, pointing to a successful fundraising month in April for the campaign, and the $15 million they raised on a New York City-area swing last week.

“I guess Romney does not disassociate himself from Trump, for same reason Obama does not return Bill Maher's million bucks,” said former McCain adviser Ana Navarro. “They hope to keep the money but not be held accountable for the outrageous idiocies that come out of these donors' mouths.”

But Navarro said Romney is, to an extent, held hostage by Trump: “[The] venom Trump would spew if unceremoniously disinvited, would be hard to control and make media fodder for days.”