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According to most recent polls, Donald Trump has a significant lead in the state, trailed by Sens. Ted Cruz and Marco Rubio.
Former Florida Gov. Jeb Bush has hovered around fourth place, with a surging Ohio Gov. John Kasich and retired neurosurgeon Ben Carson close behind.
The race in the state has been particularly nasty, with accusations of foul-play flying between multiple campaigns.
The Rubio campaign, for instance, criticized Cruz's campaign for allegedly making robocalls suggesting Rubio may drop out of the race. But the Bush campaign shot back that it was skeptical of the Rubio campaign's claim - and that it had reason to believe the Rubio campaign was spreading rumors about the Bush and Kasich campaigns in the state.
Polls close at 7 p.m. EST.