The pro-Obama super-PAC Priorities USA Action and the Service Employees International Union (SEIU) have invested heavily in Spanish-language attack ads against Mitt Romney, and according to their numbers, those ads are working.

A memo the group will release later Thursday morning shows Romney slipping with Hispanic voters in Colorado, Nevada and Florida, the three states the group targeted with its $4 million, two-month ad campaign. 

Romney's net unfavorable rating with Hispanic voters jumped 8 points in the last two months in Colorado, 5 points in Nevada, 4 points in the Orlando market and 10 points in the Tampa Bay market, according to polling by the pro-Obama group.

While in-house polling numbers must be taken with a grain of salt, the figures if true would highlight a problem for Romney.

"They say that the truth hurts, and in this case, the truth is hurting a lot," SEIU secretary-treasurer Eliseo Medina said in a statement. "Latino voters are now saying in opinion polls that Romney's words offend them, and they're going to turn those opinions into action at the election polls on Nov. 6."

The surveys of 500 registered voters apiece were conducted by Myers Research from July 11-17 in Colorado and Florida and July 11-18 in Nevada, and had margins of error of plus or minus 4.4 percentage points.

Romney has also targeted these markets with Spanish-language ads during this period, but the group's data suggests he has had little success.

Obama now leads Romney among Hispanic voters by 70 to 25 percent in Colorado and 69 to 24 percent in Nevada, according to the memo. In Tampa and Orlando he holds 34- and 33-point leads over Romney with Hispanic voters.

An NBC News/Wall Street Journal/Telemundo poll released Wednesday showed Obama leading Romney by 67 to 32 percent with Hispanic voters, a mark that was nearly identical to his lead with the group over Sen. John McCain (R-Ariz.) in 2008. Latinos are by far the fastest-growing voting bloc, making that number a worrisome one for Romney.

Florida's Hispanic population is a diverse one: While in Orlando and Tampa most Hispanics are Dominican or Puerto Rican, in Miami the population is mostly Cuban and skews Republican.