Romney campaigning for McCain this week
The 2012 Republican presidential nominee will stump for McCain on Thursday and Friday, according to McCain's campaign. 
The former Massachusetts governor will first appear with McCain at a get-out-the-vote rally in Mesa, Ariz., an area with a significant Mormon population, before the pair take part in a business panel on the economy on Friday.
McCain, who has been crisscrossing the county to stump for vulnerable colleagues, currently leads his Democratic challenger Rep. Ann KirkpatrickAnn KirkpatrickAdam Schiff's star rises with impeachment hearings Swing-seat Democrats oppose impeachment, handing Pelosi leverage McSally gets new primary challenger MORE (Ariz.) by more than 10 points, according to the RealClearPolitics index.
McCain dropped his support for the controversial billionaire last month after a 2005 tape surfaced of Trump bragging about being able to grab women due to his celebrity.
The Arizona senator also criticized Trump for refusing to say he would accept the election results if he loses, noting conceding after losing is the "American way."
Romney endorsed McCain's reelection bid in December during a stop in Arizona. He carried the state in the 2012 election, defeating President Obama by roughly 10 points. 
Romney also stumped for Sen. Mark KirkMark Steven KirkWhy Republicans are afraid to call a key witness in the impeachment inquiry Ex-Rep. Duffy to join lobbying firm BGR Bottom Line MORE (Ill.), a vulnerable Republican facing an uphill reelection battle, earlier this month.