As eight senators huddled behind closed doors to craft a bipartisan and comprehensive immigration-reform bill, South Carolinians began seeing television ads bashing Republican Sen. Lindsey Graham for his involvement. "Who elected Graham to demand amnesty and welfare for millions of illegal aliens?" a faceless voice asked in the February ad paid for by advocacy group NumbersUSA.

Who would get welfare and other benefits under immigration reform is a complicated and still-unanswered question, with Congress far from done debating immigration legislation. But what Americans think of the idea is suddenly much clearer.

According to the latest United Technologies/National Journal Congressional Connection Poll, more than two-thirds of all Americans and nine out of every 10 Republicans oppose making legalized immigrants "eligible for government benefits ... before they become citizens," confirming the issue's potency as one of the main political attacks against immigration reform supporters in 2014.

NumbersUSA’s February ad against Graham may have been an early shot, but given how strongly the message tests, it seems sure to crop up again -- assuming attention remains focused on the issue.

Overall, 77 percent of respondents opposed making government benefits available to legalized (but noncitizen) immigrants.

In findings that are sure to feed a core conservative fear about the issue, the idea was broadly unpopular across party, race, and class lines:

• Ninety percent of Republicans opposed it, as did 80 percent of independents and 65 percent of Democrats, suggesting the message could appear in general-election advertising as well as in GOP primaries.
• Nearly two-thirds of nonwhites stood against the idea, as well as 84 percent of whites.
• While college-educated women were the group of whites that most supported extending benefits, 71 percent of them still opposed it.

When asked specifically if legalized immigrants “should be eligible for health care assistance under the Affordable Care Act, also known as Obamacare, before they become citizens,” the margins narrowed thanks to heightened Democratic, nonwhite, and college-educated support -- but respondents still remained hostile to the idea:

• Sixty-nine percent of respondents said no, including 88 percent of Republicans and 72 percent of independents.
• Fifty-four percent of Democrats said no, while 43 percent said legalized noncitizens should be Obamacare-eligible.
• Among nonwhites, extending access to Obamacare polled exactly the same, while whites opposed it 76-20.

The Congressional Connection Poll was conducted by Princeton Survey Research Associates International from June 20 to 23. It surveyed 1,005 adults by landline and cell phone and has a margin of error of plus or minus 3.6 percentage points.

In the current version of the Senate’s immigration bill, most legalized immigrants who are not permanent residents will not be eligible for means-tested benefits like the subsidies in the health care reform law. Permanent residents would immediately get access to some programs, such as the health care subsidies, but would have to wait longer to participate in others, like Medicaid.

The figures illustrate the political danger in omnibus reform legislation, such as the Senate immigration bill that’s expected to pass this week, that packages popular ideas with less popular ones. In a way, it’s reminiscent of the Obama health care law itself, which features well-liked insurance regulations alongside other items that Republicans have used effectively against Democrats, such as the “$700 billion in Medicare cuts” featured in so many of last year’s campaign ads.

What immigration reform has going for it, though, is that its main elements are broadly popular: Last week’s United Technologies/National Journal Congressional Connection Poll found big majorities -- including majorities of Republicans -- in favor of allowing illegal immigrants who meet certain requirements to stay in the country and later apply for citizenship. And a strong plurality supported focusing the immigration system on acquiring needed job skills for the economy, as have the members crafting the Senate legislation. (However, 49 percent of Republicans did say this week that they would be less likely to vote for their U.S. representative or senator if he or she voted for a pathway to citizenship.)

Former Commerce Secretary Carlos Gutierrez, who heads the Republicans for Immigration Reform super PAC, said that pro-reform Republicans can survive tough messaging -- like the government benefits issue -- by focusing on the anticipated benefits, such as a lift to the economy. Republicans for Immigration Reform has also been on TV in South Carolina, with an ad featuring a local chamber of commerce official praising Graham for helping bring the economic benefit of immigration reform to the Palmetto State.

“You hear very little about the most important part” of the legislation, Gutierrez said.

“It'll be a tremendous surge for our economy,” he continued, noting that’s where his group will focus its efforts defending GOP supporters of the reform bill.

That message will have to compete with a broadly unpopular attack gaining steam among conservative opponents, though, picking away at the bill at its weakest points.