(CN) - As they hurdle headlong toward Super Tuesday, candidates for the Republican presidential nomination have largely defined themselves in the electorate's collective mind and are waging what amounts to a national "get out the vote" campaign.
Meanwhile, in South Carolina, where the Democrats will hold their presidential primary on Saturday, Sen. Bernie Sanders has arrived to challenge former Secretary of State Hillary Clinton, who seems to have doubled down in exciting her base in every possible way.
"We're in the race to win it and I think we're going to pull off an upset," Sanders said Wednesday.
Donald Trump has won three of the first four Republican contests in New Hampshire, South Carolina, and on Tuesday night in Nevada, losing only the Iowa caucus to Sen. Ted Cruz of Texas by tapping into populist anger at the Washington establishment.
On the campaign trail, even Trump has professed surprise at what has occurred since he announced his candidacy on June 16, 2015.
"Who knew this was going to happen?" Trump said last week. "I've won a lot in my life. But I never figured I'd be so far ahead. I figured I'd be in the pack and eke it out at the end."
"I didn't know this was going to happen," he said. "But here we are ... we've packed every single event, and we have a movement going on that's so special, they're talking about it all over the world."
After each of his wins, Trump has marveled at his apparent across-the-board appeal to Republican voters, winning even the evangelical vote in South Carolina that was supposed to be the core of Cruz's support.
"We've won every single category," he said.
"Rich/poor, fat/thin, tall/short ... we've won among women. We've won among men. We've won among highly educated people and among smart people that don't have the big education ... "
Trump, who said that by the end of February he will have spent $25 million of his own money on his campaign, said each of his victories buoys his cause.
"The bigger the mandate, the better it is, and the easier job we're going to have," he said while stumping in South Carolina.
By comparison, Cruz, who began his bid for the presidency a Tea Party favorite on a fervent, largely Christian-based crusade, has seen his fortunes plummet after a series of questionable campaign moves that brought persistent attacks on his integrity from both Trump and Florida Sen. Marco Rubio.
Cruz's tactics included campaign calls to voters in Iowa, telling them that the other conservative Christian candidate in the race, Dr. Ben Carson, had ended his campaign; a campaign ad that featured photo-shopping Rubio's head onto the body of another man who was shaking President Barack Obama's hand; and most recently, circulating a video on Twitter that purportedly showed Rubio disparaging the Bible.
The accusation against Rubio was false, and Cruz fired his chief spokesman, Rich Tyler, who circulated the video.
Rubio has tried to position himself as a true conservative and the only candidate in the race with foreign policy experience, which he acquired as a member of the Senate Foreign Relations Committee and the Senate Select Committee on Intelligence.