President Barack Obama is having Mitt Romney over for lunch on Thursday, and their meeting is already generating a lot of buzz. Here are five theories about the White House’s motives.

Obama and Romney were bitter rivals in the 2012 presidential campaign, with Obama getting a surprisingly big victory in the Electoral College.

Since then, Romney has stayed out of the spotlight, while Obama said he would invite Romney to the White House at some point.

The pair will have a private meeting for lunch, so there will be no press coverage or a photo opportunity.

So here are five theories that are floating around about the get-together.

1. Obama is extending a common courtesy

In 2008, President-elect Obama met with John McCain on November 17 in Chicago, and there was a photo op with the two men. McCain had lost to Obama, but he was still a U.S. senator.

At the time, McCain said he would “obviously” help the incoming president, and the former foes issued a statement about bipartisanship.

Conditions are different in 2012, with Romney not holding a Senate position and Obama sitting in office as the incumbent.

We’re also not sure that there is a tradition of losing presidential candidates meeting with incumbent presidents.

The protocol for current presidents meeting with former presidents is entirely different.

You can read excerpts from a book called “The President’s Club” for a look at how presidents interact.

2. Obama will offer Romney a Cabinet job

That doesn’t seem likely, since Romney is self-supporting financially and has a life outside politics, with 18 grandchildren.

If a job were forthcoming in the new Obama Cabinet, it would have to be approved by the U.S. Senate, with a majority vote.

Since the Senate is controlled by the Democrats, that could get interesting.

Also, as a Cabinet member, Romney would be reporting to Obama, which also would be interesting, given the mutual dislike between the candidates on the campaign trail.

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3. Obama will enlist Romney in the fiscal cliff debate

One issue where the candidates disagreed sharply on the campaign trail was on the fiscal cliff debate.

Romney was not in favor of raising taxes on higher income earners, because he believed it stunted the growth of business and hurt its ability to create jobs.

Obama was critical of Romney’s philosophy about the fiscal cliff, especially his attacks on entitlement spending.

However, one of Romney’s ideas on the campaign trail, a cap of income tax deductions for wealthier Americans, might become part of the negotiations in Congress in December.

Obama had floated out a similar plan in the past, but just after the election, Senate Democrats attached Romney’s name to it, as a way to get the Republicans to discuss it.

“Let’s just say there’s a renewed interest,” said Senator Kent Conrad, Democrat of North Dakota and chairman of the Senate Budget Committee, as reported in The New York Times on November 13. “Part of it is people reflecting on Obama’s proposal, but when Romney said what he said, it just added fuel.”

4. Obama wants Romney’s advice on business issues

That’s also a distinct possibility, since President Obama praised Romney’s business acumen after the campaign.

“He presented some ideas during the course of the campaign that I actually agree with. And so it’d be interesting to talk to him about something like that. There may be ideas that he has with respect to jobs and growth that can help middle-class families that I want to hear,” Obama said.

Of course, President Obama has scores of business advisers already, including friends in the private sector.

5. Obama wants closure on the 2012 presidential election, or something else?

President Obama said after the election that he was interested in talking with Romney about ways the two men could work together.

He used similar words about John McCain in 2008, after Obama easily defeated the Republican candidate. That didn’t come to pass.

One theory is that Obama could just want to be consistent in how he publicly handles his consecutive wins in 2008 and 2012, and it would be a slight to Romney if he didn’t extend a similar invitation for a sit-down meeting.

But in an editorial in Wednesday’s Washington Post, former Romney strategist Stuart Stevens paints a portrait of Romney as a good man who is a Washington outsider, who was never accepted by the GOP establishment.

“I appreciate that Mitt Romney was never a favorite of D.C.’s Green Room crowd or, frankly, of many politicians. That’s why, a year ago, so few of those people thought he would win the nomination,” Stevens said.

Given that some key Republican leaders criticized Romney for his post-election comments about Obama using “gifts” to win the election, could Obama approach Romney about some kind of position related to bipartisanship or public service?

As odd as the idea sounds, Romney has made it clear he’s done running for public office, but has no plans to retire.

An Associated Press story earlier this month cited a Romney insider as saying the former candidate had an interest in philanthropic efforts or having a role in future Olympics efforts.

Scott Bomboy is the editor-in-chief of the National Constitution Center.