A Democratic super PAC supporting President Barack Obama and one of the nation's largest unions are launching a joint $4 million Spanish-language advertising campaign targeting Hispanic voters.

The ads, sponsored by Priorities USA Action and the Service Employees International Union, argue Republican presidential candidate Mitt Romney's policies would benefit the wealthiest Americans at the expense of Hispanics and other working families.

Priorities USA Action was founded by two former Obama White House aides. It has struggled in fundraising compared with Republican-leaning super PACs like American Crossroads and its nonprofit arm, Crossroads GPS. But Priorities USA's partnerships with SEIU and other organizations have helped it compete with the better funded political action committees.

The ads will run on television and radio stations in Colorado, Nevada and Florida throughout the summer.