Sarah Palin, McCain's vice presidential running mate who has faced mounting criticism over her family and political past, is expected to address the convention on Wednesday.
Other speakers include Fred Thompson, a former actor and senator for the state of Tennessee and Joseph Lieberman, former Democratic and now independent senator.
Meanwhile police on Tuesday said they arrested 286 people during Monday's mainly peaceful protests, in which around 10,000 people marched.
Small groups of protesters broke off from the main march and broke windows, slashed tires and harassed delegates, police said.
Protesters countered that police were heavy-handed, after several journalists were also detained and pepper spray was used on some marchers.
McCain's allies on Tuesday also hit back at critics after Palin, a social conservative opposed to abortion, announced that her unmarried teenage daughter was five months pregnant, accusing the campaign of Barack Obama, the Democratic presidential hopeful, of sexism.
|Palin's perceived lack of experience has been scrutinised [Reuters]
Questions have also been raised over Palin's lack of experience and the news that she has hired a lawyer to defend her in a probe over possible abuse of power in the state of Alaska, where she is governor.
It was alleged that she fired the Alaskan state public commissioner because he reportedly refused to fire her brother-in-law.
"I am appalled by the Obama campaign's attempts to belittle Governor Sarah Palin's experience," Carly Fiorina said in a statement on Tuesday.
"The facts are that Sarah Palin has made more executive decisions as a mayor and governor than Barack Obama has made in his life."
Obama on Monday had criticised Palin saying that his own campaign had shown its ability to manage "large systems", while Palin's former mayoral seat in Alaska, Wasilla, had only 50 employees.
"We've got 2,500 in this campaign. I think their budget is maybe $12 million a year ... we have a budget of about three times that just for the month," he told CNN.
Al Jazeera's Rob Reynolds in St Paul says the focus on McCain has been diverted by questions over Palin, who was supposed to appeal to the moderate or independent voters that McCain has been trying to woo from the Democrats.
Republicans are also concerned that McCain's choice of Palin may lead to awkward questions over whether she was properly vetted, as well as queries over McCain's judgment and his own fitness and experience for office.
Republican leaders said they would go ahead with a programme of emphasising McCain's experience, particularly following his time as a former Vietnam prisoner of war.
In addition, Lieberman, himself a former Democratic vice presidential nominee, will discuss American "exceptionalism" in his remarks.
However, the programme for Wednesday and Thursday is still being worked on, officials have said.
McCain had ordered a curtailing of the conventions events on Monday as Hurricane Gustav swept over the state of Louisiana.
However, the storm missed the city of New Orleans, devastated by 2005's Hurricane Katrina.