Boston ? Barack Obama’s opponent four years ago was a Republican who repressed his moderate and liberal instincts, who insisted he was a conservative, who seemed to be suffering from a political identity crisis, who had a sterling resume but a halting campaign style.

His opponent this time can be described … exactly the same way.

So we’re familiar with what the Republicans will be peddling this time, though the name at the top of the GOP ticket won’t be John McCain but Mitt Romney. The Democrats, of course, will be trying to sell Barack Obama again.

The story of the 2012 campaign may not be that the characteristics of the Republican candidate have changed. The story may be that the same Democratic candidate is entirely different.

Last time, Barack Obama was an insurgent. This time he is an incumbent. Last time he was an outsider with hardly any experience. This time he is an insider with a record to defend. Last time he ran as a critic of administration economic policy. This time he is running as the spokesman of administration economic policy. Last time he pushed to suggest he was like Abraham Lincoln. This time he is working against the notion he is Jimmy Carter.

Nominees found lacking

While Republicans, especially conservatives, bemoan the fact that they will be running a nominee much like the last one, Democrats, especially liberals, bemoan the fact that they don’t have the shiny, inspiring new political figure of 2008 to offer.

Presidents running for re-election in times of crisis — Woodrow Wilson in 1916, Franklin Roosevelt in 1936, Richard Nixon in 1972, Ronald Reagan in 1984 and George W. Bush in 2004 come to mind — often pave the way to a second term by appealing to public reluctance to make a change in a period of peril. As Obama’s Illinois predecessor said at the Republican convention in 1864, in the middle of the Civil War: It’s best not to “swap horses while crossing the river.”

But you won’t hear warnings about changing horses from the Democrats this year. Obama was the kind of candidate who inspired voter loyalty, but he is not the kind of president who does.

Which is why professionals on both sides of the 2012 election are so uneasy. The Republicans aren’t comfortable with their nominee and the Democrats worry that the voters aren’t comfortable with theirs.

There hasn’t been a re-election battle like this since 1932, when — and this is largely forgotten now — the Republicans knew Herbert Hoover was vulnerable and the Democrats worried that FDR was neither ready for, nor up to, the job.

Incumbents like Hoover often portray their challengers as being too inexperienced for the White House, but that is an argument peculiarly unsuited this year to the Democrats, whose candidate ascended to the White House after only four years in the Senate.

One modern president, Ronald Reagan, managed to remain an outsider even when he was inside the White House. All the rest, including Jimmy Carter and George W. Bush, both of whose personal impulses veered against insider Washington, found themselves running for president as insiders. In Carter’s case, it didn’t work. In Bush’s, it did.

Insiders or outsiders?

For Obama, the situation is more complex. As a black president, he is by definition an outsider. In his memoir, he spoke eloquently of knowing “how to live as an outsider.”

But this year, Obama has relentlessly portrayed himself as a presidential insider, with insider knowledge and insider perspective if not with an insider personality. David Maraniss, in his forthcoming biography of the president, speaks of the contrast between the young Barack Obama and an early girlfriend, a child of wealth whose family owned a country estate in Connecticut. “The ironic thing,” the woman said, “is he moved through the corridors of power in a far more comfortable way than I ever would have.”

Romney, the son of a governor, corporate executive and Cabinet member, is a natural insider, even a born insider — but in this election he will be the outsider.

That’s not the only unusual thing about his profile as he looks toward November.

Romney is a nominee all but certain to lose his own state, a feat accomplished only twice by candidates who eventually won the election (Woodrow Wilson in 1916, James Polk in 1844). So popular is Obama here in Massachusetts that Democratic Senate candidate Elizabeth Warren’s television commercials prominently feature the president, something you will not see everywhere, or maybe even anywhere else.

There are scores of scenarios for the fall election, but one that seems stubbornly persistent focuses on a state that Franklin Roosevelt won by a stunning three-to-one margin in 1932 and that held the balance of power in the contentious election of 2000: Florida.

Past performance, as Wall Street financiers often say, is no indicator of future returns, but if the Democrats carry the states that have become reliably Democratic in recent elections, they would need only Florida to win the 270 electoral votes required to keep the White House.

Florida factors

Now, consider three very important indicators: Florida’s job growth in the past year, at 1.24 percent, is precisely at the national average. Florida’s unemployment rate, at 9 percent, is higher than the national average of 8.1 percent. And the latest Quinnipiac University poll shows the two presidential contenders at a virtual dead heat in the state, with Romney holding a statistically insignificant lead of 44 percent to 43 percent over Obama.

That reinforces the notion that this will be a terrifically tight election, the sort that could hinge on a gaffe or an unpredictable remark. Political professionals, who by nature like to control events rather than be vulnerable to them, hate this sort of situation. It renders doctrines dormant, and it turns politics inside out.