WASHINGTON (AP) - Republican Chuck Hagel is to be the lone witness today as the Senate Armed Services Committee holds a hearing on his nomination for defense secretary.
    
The former two-term senator from Nebraska will face critics in his party who have challenged his past comments on Israel, Iran and nuclear weapons. Hagel is a decorated Vietnam combat veteran and would be the first enlisted man to serve as defense secretary. President Barack Obama tapped Hagel to succeed Leon Panetta.
    
Crucial for Hagel will be the questioning by another Vietnam veteran, Arizona's Sen. John McCain. Hagel and McCain once hand a close relationship when the two were in the Senate, but politics and Hagel's opposition to a troop increase in Iraq divided them.