I was playing a MTT on FTP this morning and this hand came up:

Blinds 120/240, 9-handed


UTG+1&2 limp, fold, MP+1 limps with , and button pops to T1000

Blinds and UTG+1 fold. UTG2 and MP+1 call.

Flop: with pot of ~3800

Action checks to button, who pushes for T3100. UTG2 folds. With about T5000 more than the allin, what is MP1's action?