If Romney loses, the GOP will have to go through a painful process of self-examination If Romney loses…

For Republicans, the only thing harder than losing to Barack Obama might be explaining it.

By any reasonable standard, Obama is a seriously vulnerable incumbent: a president overseeing a limping economy, whose party got thumped in the 2010 midterm elections and whose signature accomplishment of health care reform is highly controversial. Whatever his strengths on national security and personal likability, Obama probably began the 2012 campaign as the most beatable sitting president in 20 years.


( Also on POLITICO: If Obama loses …)

So if Obama manages to defeat Mitt Romney on Tuesday, the Republican Party will have to go through a painful process of self-examination and internal debate in order to explain what went so badly wrong.

The debate won’t just be fodder for political obsessives: It will also determine how Republicans approach governing next year and how the party campaigns in 2014, 2016 and beyond.

Even before tomorrow’s vote, the post-election arguments about why Romney lost — if he does — are beginning.

( PHOTOS: Final countdown to Election Day)

Here’s a POLITICO preview of the top arguments Republicans would use to explain and excuse it:

Mitt Romney was a historically bad candidate

If Romney wins on Tuesday, he’ll be president of the United States. If he loses, he’ll be the fall guy for the entire Republican Party.

Republicans weren’t overjoyed about nominating Romney in the first place, partly because he was a shade too moderate for their taste, but also because he was such an inept competitor in the 2008 primaries.

Win or lose, Romney has validated many of those fears, careening from misstep to misstep throughout the 2012 race. If Romney wasn’t fumbling his response to the Supreme Court’s Affordable Care Act ruling, he was offending the British on the eve of the London Olympics or getting caught on tape bashing Americans who don’t pay income taxes.

( Also on POLITICO: The looming GOP civil war)

On a deeper level, Romney was a problematic candidate for 2012. In a campaign still shadowed by the meltdown of the financial services industry, the GOP picked a candidate as close to Wall Street as any in history. Former Mississippi Gov. Haley Barbour said in August that Democrats had branded Romney as a “wealthy plutocrat married to a known equestrian.” He was right, and Romney may have been more vulnerable to such attacks than any other major Republican in America.

Relentlessly attacked by Democrats for his Bain Capital record, Romney never responded in an effective way. He stuck to his script that Obama hadn’t successfully steered the economy back to solid ground, failing to flesh out his own agenda until late in the game and even then only vaguely.

If Republicans come up short in Senate or House races, too, they’ll gripe about the lack of Romney coattails. It probably won’t be fair for the party to blame Romney for all its failings down-ballot, but it’ll happen anyway.

Oh, Sandy

Over the weekend — days before the election ends — Republicans were already pointing to Hurricane Sandy to explain a Romney loss. The argument goes like this: Wall-to-wall news coverage of the superstorm, combined with the loss of life and uncertainty about how to campaign in the shadow of a tragedy, stalled Romney’s momentum.

Obama took charge of storm-relief efforts, visiting hard-hit sites, and Americans tend to rally around the president in a crisis. The glowing praise for Obama from New Jersey Gov. Chris Christie, a top Romney surrogate, also didn’t help the Romney cause.

Karl Rove told The Washington Post that the storm allowed Obama to be a “bipartisan figure this week. His has been the comforter-in-chief and that helps.” Barbour told CNN’s Candy Crowley that the storm “broke” Romney’s momentum.

And News Corp. Chairman Rupert Murdoch attacked Christie on Twitter, declaring that he “must re-declare for Romney, or take blame for [the] next four dire years.”

There’s no question that the storm has aided Obama in terms of media coverage, and praise from the opposing party is always useful. But Christie’s power to swing an election — one largely being fought in Midwestern states unaffected by the storm — is seriously questionable. So, too, is the idea that Romney was assured victory in a tight, 2-point race before the storm hit.

We can’t know what would have happened if the storm hadn’t hit. But there were strong indications before it landed the week before the election that Romney’s momentum was stalling, and that the Republican had failed to capitalize on his strong first debate performance with enough gusto.

What’s more, had Romney run a more effective campaign over the past year, he wouldn’t have had so much riding on the last month of campaigning — and a single blown debate by Obama — to vault him over the top.

Stuart Stevens blew it

Every time Romney has flagged in the 2012 race, a chorus of conservative critics have directed their ire at Stuart Stevens, the flamboyant Mississippi native and auteur who serves as Romney’s chief strategist. The last man standing after a messy internal fight among Romney’s 2008 advisers, Stevens was a target from the beginning.

Stevens’s basic methodology for winning races goes like this: run a center-right candidate through a Republican primary by focusing on the general election, then focus relentlessly on the incumbent while taking as few specific policy positions as possible.

This approach appears to work better in statewide races than it does in a presidential campaign, when voters seek more specificity and a genuine personal connection with their candidates. Yet Stevens never strayed from this strategy, leaving Romney largely undefined to the national electorate as Democrats tore up his record at Bain Capital and as governor of Massachusetts.

Stevens was the chief speech writer, traveling strategist, ad-maker and overseer of the campaign’s in-house ad buying strategy. Romney’s convention speech, prepped on the fly, made a rookie mistake by omitting a reference to the Afghanistan War. Romney’s ads were criticized as banal, cookie-cutter pieces that never broke through. The ad-buying strategy, reviewed at length by POLITICO, left Romney outflanked by the Obama campaign in key markets across the country.

To be sure, Stevens is not the only person in Romney high command who would (and should) take blame for a loss. But as a favorite punching bag for conservatives throughout the cycle, there’s no doubt he would be a whipping boy on Nov. 7.

Immigration was a fatal blunder

It’s been one of the most consistent — and for Republicans, alarming — features of 2012 polling: Romney is getting blown out with Latino voters. And he pretty much made his own bed with this powerful and growing demographic.

As early as September 2011, when Romney was running to Rick Perry’s right on immigration — Romney’s most memorable line on the subject was that illegal immigrants should choose to “self-deport” to their native countries — Republicans privately fretted that Romney was digging himself a demographic hole.

They were right: Romney’s likely to lose Latinos by a wider gap than McCain’s 36-point margin of defeat. That could push states like Nevada, Virginia, Florida and Colorado into Obama’s column, and if Obama wins just a few of those battlegrounds, it will be exceptionally difficult for Romney to win nationally.

Should that scenario come to pass, Republican elites — who have long feared confinement to an aging and white voter base — will be ringing the alarm bells Wednesday morning. Some party leaders haven’t waited until after Election Day to raise the hue and cry.

In an interview with New York magazine, former Florida Gov. Jeb Bush compared the party’s predicament with Latinos to Monty Python’s hapless Black Knight: “We’re competing with ninjas, you know, guys with big, sharp knives, and we have no weapon, and we’re playing like we’re fighting them, and we get an arm cut off — ‘Oh, it’s just a flesh wound’ — and we’re down to the trunk.

It was a mistake to nominate a moderate — again

For much of the Republican base, the past four years carry a straightforward lesson: When you nominate an ideological squish like John McCain, you lose. When you run on big, bold, conservative ideas — as the party did in 2010 — you win.

Romney has embraced many of the ideas of the 2010-vintage GOP, selecting Paul Ryan as his running mate and embracing staunchly conservative goals like defunding Planned Parenthood. But for most on the right, Romney remains the “Massachusetts moderate,” as Newt Gingrich christened him during the GOP primaries.

Back in the Republican nomination fight, Rick Santorum called Romney the “worst Republican” to put up against Obama, since he couldn’t draw a bright-line contrast on health care and other issues. Should Romney lose on Tuesday, this argument will be back in force.

There are a bunch of holes in this argument. Romney has taken serious damage with women and Latinos as a result of hewing to the conservative line on abortion and immigration. It’s a dubious proposition that Romney would be better off campaigning harder on issues like privatizing Medicare.

But in the race’s final month, old Mitt — the one who passed universal health care in Massachusetts as governor — seemed to re-emerge on the campaign trail, promising no tax cuts for the wealthy and that government can indeed do good things. It was his strongest month of the campaign.

Where Romney has clearly fallen short is offering up a compelling positive vision for the country, not necessarily a compelling, orthodox conservative vision. His longtime conservative critics will still whack him on this count with verve.

It was all the media’s fault

Claims of media bias from both sides are nothing new in presidential politics. But the Romney campaign has long lamented that the press is out to get them, with the candidate, his wife and top surrogates openly complaining that they can’t get a fair shake.

Romney and his campaign have viewed their press coverage as routinely savage, feeding into the Obama campaign’s caricature of Romney as a non-mustachioed Snidely Whiplash. Reporters, the Romney team has complained, are more interested in gaffes than in policy, even if that means taking Romney out of context.

Yet the reality is Romney also did little to make an affirmative case for his candidacy and his character until late in the game. When the Obama team attacked, Romney and his spokespeople resisted responding to the press, declining to comment on stories and then attacking them as biased and factually flawed only after they appeared in print.

For most of the 2012 cycle, Romney’s campaign invested little energy into making its case to and building relationships with the national media. Romney conducted relatively few interviews, favoring softball appearances on Fox News and interviews with radio hosts like Hugh Hewitt. His spokespeople didn’t reliably answer press requests, even benign ones. The assumption was that the press is either irrelevant or simply trying to cause trouble.

But treating the media as a hostile force can be a self-fulfilling prophecy: Denying reporters basic access and refusing to answer straightforward questions about policy and strategy are a pretty surefire way to deprive yourself of positive coverage.

Democrats have complained about the media, too, attacking the press covering the 2012 campaign for not fact-checking Romney aggressively enough and for buying in too credulously to the “narrative” of Romney’s October momentum. But few on the left have made these complaints a primary explanation for the state of the race.