DES MOINES, Iowa (AP) – Rougher shoving and sharper jabs are expected as a tighter field of Democrats takes the stage for Tuesday night’s final debate before Iowa’s leadoff presidential caucuses. Just six candidates are gathering in Des Moines. That’s the smallest number yet on a debate stage. The new dynamic will offer candidates more opportunities to criticize each other’s proposals as well as tout their own. But the fuel for the fire comes from the fact that it’s the last debate before Iowa’s results, which will give the winner momentum for the primaries to come. State polling shows Iowans’ preferences too close to call.