President-elect Barack ObamaBarack Hussein ObamaMattis denounces Trump, applauds protests, defends America On The Trail: Crisis response puts Trump on defense, even in red states The Hill's 12:30 Report: NYT publishes controversial Tom Cotton op-ed MORE and his former rival, Arizona Sen. John McCainJohn Sidney McCainKelly holds double-digit lead over McSally in Arizona: poll Montana barrels toward blockbuster Senate fight How Obama just endorsed Trump MORE (R), will meet at noon EST today in Chicago for meetings.

McCain will be joined by key ally Sen. Lindsey GrahamLindsey Olin GrahamBill aims to help farmers sell carbon credits Graham postpones Russia probe subpoena vote as tensions boil over Graham pushes back on Mattis criticism of Trump: 'You're missing something here, my friend' MORE (R-S.C.) while chief of staff-designate Rahm Emanuel will round out the meeting.

"It's well known that they share an important belief that Americans want and deserve a more effective and efficient government, and will discuss ways to work together to make that a reality," the Obama-Biden transition team said Monday.