His backers take offense to new party rules.
"This is obviously the biggest speech of my life," Mrs. Romney said.
The campaign played down talk that Romney will see a post-RNC jump in the polls.
Strategist says it will be about "what his presidency would look like."
The New York Roman Catholic leader made the announcement Tuesday through his spokesman.
As students return to campus, President Barack Obama's campaign will be there waiting for them.
Antonio Villaragosa said the GOP "can't just trot out a brown face or a Spanish surname."
The New Jersey governor, who will give keynote Tuesday, rebutted speculation about turning down a VP offer.
The candidate's remark is certain to raise questions about his position among conservatives.
Time cutbacks have given new momentum to questions about whether to modernize the quadrennial affairs.