Rarely have the stakes been so high in a race for second place.

Barring a seismic shift in voter sentiment, Donald Trump is expected to dominate the Republican primary field on Super Tuesday, adding to his already-sizable delegate lead – but Marco Rubio and Ted Cruz are battling fiercely to be the definitive alternative to take on Trump in what could be a bruising, to-the-convention fight for the future of the party.

Ohio Gov. John Kasich, who's expressed low expectations for Super Tuesday -- though his presence continues to frustrate efforts by Rubio and Cruz to consolidate support -- remains in the race in hopes of making it to the Ohio contest in two weeks.

“Super Tuesday was never anything that we ever thought was going to be some great thing for us,” Kasich openly acknowledged to Fox News on Tuesday, also telling Fox Business Network there's "zero chance" he'd be anyone's running mate. 

Rubio, too, is looking ahead to the March 15 contest in his home state, even planning to hold his primary night rally there Tuesday.

But first, he’ll need to stay competitive with Cruz in the 11 Super Tuesday states awarding 595 total delegates.

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There’s at least one state he stands a decent chance of winning, according to recent polling, and that is Minnesota. Rubio was holding a rally there Tuesday before heading to Miami.

Cruz, meanwhile, is the odds-on favorite in his home state of Texas – which, with 155 delegates, is the biggest prize of the night. In a sign of his expectations, Cruz planned his election night party in Stafford, Texas.

But because delegates can be allocated proportionally in the Super Tuesday contests (provided the winner’s margin of victory is not colossal), Rubio and Cruz both want to rack up a substantial number of second-place finishes.

A Rubio campaign aide told Fox News they are "focused on only one thing today: delegates."

The polling is varied and in some states sparse, but RealClearPolitics averages show Cruz and Rubio likely are competing closely for second place in Georgia, Tennessee, Oklahoma and elsewhere. Rubio appears to have the edge over Cruz in Virginia and Massachusetts, while Cruz was actually leading one recent poll in Arkansas.

In the run-up to Tuesday, Cruz and Rubio both have stepped up their attacks on the front-runner, resorting to the kinds of personal insults and attacks that have defined Trump’s campaign style.

Rubio defended the new tack in an interview with Fox News.

“Every now and then, someone like that needs a taste of their own medicine because that's called a bully and he’s using the pulpit of the presidency or the presidential run to insult people,” Rubio said.

Cruz told Fox News that while Trump will have a “big chunk of delegates” come Wednesday morning, “We're going to have a big chunk of delegates, and there's going to be a huge drop off for everybody else.”

Trump, for his part, suggested Tuesday he wants to see Rubio “get out” of the race.

“He hasn’t won anything,” Trump told Fox News. As for Rubio’s goal of a big win later this month in Florida, Trump said, “I don’t think right now he could be elected a dogcatcher in Florida.”

Trump wasn’t conceding the race against Cruz for Texas, either.

Retired neurosurgeon Ben Carson, meanwhile, defended his continued presence in the race on Tuesday.

“People have asked for somebody who is not a politician, who was a member of we the people, who has an outstanding life of achievement and who thinks the way they do,” he told Fox News.