(CN) - Presidential hopefuls crisscrossed the battleground states of Ohio, Florida, North Carolina, Missouri and Illinois on Monday, making last-minute appeals to potential supporters in the hectic, fleeting hours before what could be a game-changing day of primaries Tuesday.
The biggest prizes for the Republican candidates on Tuesday are the delegate-rich, winner-take-all states of Florida, where the winner will claim 99 delegates, Illinois, where the winner will garner 69 delegates and Ohio, where the winner will walk away with 66 delegates.
Missouri, another winner-take-all state, has 52 delegates at stake, and in North Carolina, where the delegates will be divvied out proportionately, the candidates will be vying for a share of 72 delegates.
As for the Democrats, 214 delegates are at stake in Florida, while 143 are in play in Ohio.
In the other states voting Tuesday, 156 delegates will be at stake in Illinois, 107 in North Carolina, and 71 in Missouri.
But it's the Republican race that's under the most intense scrutiny. Big wins by the frontrunner, Donald Trump, would all but eliminate two of his rivals, Sen. Marco Rubio of Florida and Ohio Gov. John Kasich, and make the race for the Republican nomination a two-man affair with Trump facing off with Sen. Ted Cruz of Texas, probably all the way to the floor of the party's nominating convention.
The latest Marist/NBC/Wall Street Journal poll show Trump holding a double-digit lead over Rubio in Florida, 43-22 percent. The same poll shows Rubio and Cruz in a statistical tie for second place.
Taking the political temperature in Ohio, the Marist/NBC/Wall Street Journal poll finds Kasich will a slight edge over Trump, 39-33 percent. Other polls show the two men essentially tied.
Meanwhile, a Quinnipiac University released Monday suggested Sen. Bernie Sanders of Vermont is closing the gap between himself and Hillary Clinton. She now leads him in the poll 51-46 percent, but a month ago she was up by 30 points.
Douglas Schoen, the veteran pollster, author and commentator and political analyst for Fox News offered his assessment of what might play out Tuesday to Courthouse News Monday afternoon.
"If John Kasich doesn't win Ohio, he'll be out of the race. If Marco Rubio doesn't win Florida, he'll be out of the race," Schoen said.
"Hillary and Bernie, I think are going all the way to the convention," he said. "Bernie has the chance to win somewhere between one and three states tomorrow. I think Donald Trump will certainly win Florida, and potentially as many as four more states.
"If Trump wins Florida and Ohio, I think he will have a giant leg up on winning the nomination, and if he doesn't we can expect to see a long slog between he and, most likely, Ted Cruz," Schoen said.
Hoping to sure up his support heading into Tuesday contests, Rubio scheduled an "Interstate-95 Bus Tour" of the state Monday with events planned in Jacksonville, Melbourne, West Palm Beach and Miami.
Trump, meanwhile, convinced he'll soundly win Florida, turned his personal attention to Ohio. In his place, his campaign scheduled a noon rally featuring former Alaska Gov. Sarah Palin in The Villages, Fla., a community a few hours northwest of Orlando, but that event was abruptly called off.