LAS VEGAS -- It's fight night in Vegas, as the Republican contenders for the presidency meet in their fifth televised debate of the primary season. The kids' table starts at 6 p.m., while the main event is at 9 p.m. Check out the premium site for more coverage, but here are some things we are keeping an eye on tonight.

  1. Targeting Ted: The release of the Des Moines Register/Bloomberg Politics poll showing Ted Cruz leading the Iowa caucuses with seven weeks to go sent a shock wave through the field. Donald Trump quickly went on the attack, and Marco Rubio has already been hammering Cruz on national security. Cruz, so far, has refused to fight back in public -- and we will find out if he continues to hold back.
  2. Terror's long shadow: The candidates have not debated since terror attacks rocked Paris and San Bernardino, Calif. National security is sure to dominate the discussion, and we will see how much it crowds out other issues. One possible beneficiary: Chris Christie, who prosecuted terror cases.
  3. A Goldilocks task for the moderators: At the October debate, CNBC's moderator team was universally hammered by Republicans for hostile, and sometimes fumbling "gotcha" questioning. Then at the November debate, Fox Business Channel came off a bit timid. Led by Wolf Blitzer, expect CNN's team tonight to search for a middle ground -- holding the candidates to account with follow-ups, but not unloading an opposition research file.
  4. Carson slipping: Retired neurosurgeon Ben Carson has seen his poll numbers drop dramatically in the past several weeks, with much of that support going to Cruz. A commanding, knowledgeable performance on foreign affairs could help reverse the slide.
  5. Trump! New York is The Donald's home, but the glitz of Vegas better fits Trump's style. The debate is at the Venetian casino, less than a mile from the Trump International hotel. An uneven debate performer so far this year, perhaps Trump will be feeling a home-turf advantage.