Sophie Quinton bets tonight's winner won't have a mandate:
Long-shot scenarios aside, here’s what we’re more likely to see: The man who wins the White House on Nov. 6 is expected to do so by a narrow margin. Democrats are expected to hold the Senate, and Republicans are expected to hold the House. That’s not a change election; that’s an election that locks in existing dynamics.
Yglesias, on the other hand, argues that a "mandate is not a real thing, so there's nothing a candidate can do—up to and including a Democrat carrying North Carolina and Indiana—to win one":
Probably the best way to think of a mandate is as a historical artifact of the poorly sorted congressional politics of yore. Politicians in that framework were cross-pressured between partisan and ideological loyalties. A president with a "mandate"—think Ronald Reagan in 1981 or Lyndon Johnson in 1965—could unify the ideological factions within his own party while fracturing the other side's coalition. Modern politics just doesn't work like that.