GOP challenger Mitt Romney appears to be slipping behind in some key battleground states, according to a series of new polls.<br />STORY HIGHLIGHTS<br />NEW: Republican senators blast President Barack Obama and Democrats<br />Obama is appearing at Univision town hall forum in Miami<br />Mitt Romney campaigns in Sarasota, holds fund-raisers in Palm Beach<br />Florida is a key battleground state, and both candidates are fighting for the Latino vote
