And, now, a message of unity in America:

Barack Obama and Mitt Romney have something important in common.

They both believe in the power of data, expertly utilized, to win elections. (We will not consider the importance of a candidate’s capacity to inspire in this article.)

Tuesday was a bye day in this state for Obama, the incumbent with no challenger on the Democratic ticket, and as such the D’s used it as dress rehearsal for November.

The official line was that nobody was bothering with traditional get-out-the-vote operations, with the secretary of state predicting that turnout for the night’s Democratic primary would be about 75,000, or about 30 percent of what it was in 2008.

But, said Kevin Harris, who recently joined the Democratic National Committee’s press operation from the White House, “we’re testing some things. We’re showing some muscle.”

The phone bankers and the canvassers were doing their thing, calling up supporters of various stripes and knocking on doors, then marking down their responses on dense sheets that could be collated later and entered into the vast Organizing for America database that has been maintained for just this reason.

The rapid-response team at the Democratic National Committee lined up Rep. Jim Clyburn to “welcome Mitt Romney to South Carolina” on Wednesday. The e-mail invitation to this event at the State House in Columbia hinted at the particular Palmetto State hospitality only Clyburn can supply — at the point of a shiv.

The visibility people were out at polling places throughout the state. A clutch of them hollered “four more years!” and hoisted Obama signs when Newt Gingrich showed up at an elementary school in this city. Others handed out pink slips elsewhere in honor of that “I like being able to fire people” valentine that Mitt Romney had signed on Monday. At one point Tuesday, the idea was floated that the people could put on actual pink slips.

Romney gave his victory remarks and headed off to South Carolina; his headquarters in this city already had a big “For Lease” sign on it. In contrast, Organizing for America, Obama’s reelection campaign, has seven offices in the state, with more than 20 paid staffers at work in field, digital and communications operations.

“We’re here for the long haul,” said Holly Shulman, the communications director of the state Democratic Party, who was moving reporters and TV crews in and out of the campaign’s grimy warren of offices near the city waterworks, a sort of “Real World” of frenzied activity and cold pizza. And indeed, an MTV crew showed up eager to capture said grimy warren of offices, identified only by a handmade “Obama 2012” sign stuck in a window.

She ticked off data: More than 3,200 one-on-one meetings and 500 events since April.

It might have seemed that Democrats could take the day off and let the Republicans be the Bain of Romney’s existence. Gingrich charged him with “looting.” In South Carolina, Rick Perry opened up Romney’s record: “They’re vultures that are sitting out there on the tree limb, waiting for the company to get sick, and then they sweep in, they eat the carcass, they leave with that, and they leave the skeleton.”

Instead, Democrats acted like National Guard members on their monthly training duty.

The DNC had a war room above a lounge downtown; its chairman, Rep. Debbie Wasserman Schultz, raced through media appearances all day before landing at the live house party at a bar that has the distinction of selling more Bailey’s Irish Cream liqueur than anywhere else in North America.

And Megan Arsenault and Alexis Ploss ambled down the gracious streets of the North Side, a sheaf of papers and a stack of Barack Obama door-hangers in their hands, cementing their new friendship. It was a balmy day for this state in January, about 45 degrees under a pretty sky. The streets were quiet, and the people at home where they knocked were nice.

For all its trench warfare and money bombs, politics also is something to do, an activist hobby like leading the Girl Scouts or joining the volunteer fire company.

Arsenault, a 20-year-old college junior from tiny Rumford, Maine, and Ploss, 22, a hometown girl studying astrophysics at the community college, met as Obama volunteers and “became friends right away,” as Ploss put it.

It was a mixed neighborhood, meaning there were signs for Romney and Gingrich, and Jon Huntsman and Ron Paul. No Ricks, Perry or Santorum.

“Newt is such a funny name,” said Arsenault. “I think of ‘lizard’ every time. It is not a good name for politician.”

“I think of that scene in ‘Matilda’ where the newt falls in the water glass,” said Ploss. “I think it is the only movie in which a newt makes an appearance.”

They talked about their school loans, and Arsenault said she had just deactivated her Facebook page, with its 400-some friends, because “some of my friends are conservative, and I have a lot of Obama stuff on there, and I was starting to get some really mean e-mails.”

They studied their map, which wasn’t working for them; Ploss kept asking her LG Optimist smartphone for walking directions.

“Are you Celeste?” they said at one.

“Are you Sara?” they said at another.

“Are you Fern?” they asked an elderly man who opened his door, wearing a blue shirt and a tie.

“I am Fern,” he said.

“I’m Alexis, and this is Megan, and we’re volunteers for the president. We wanted to know if you voted, and if you support . . . ”

“I already did, and of course I voted for him,” said the man. “And frankly, I don’t understand why everybody doesn’t!”

They all shook hands, and the man said, “Keep up the good work, ladies!”

The young women carefully marked down their results. They walked on.

Staff writer Amy Gardner in Manchester contributed to this report.