Winning in politics isn’t everything, it’s the only thing.

But how important a factor electability should be in a voter’s calculation remains very much in the eye of the beholder, leading to an active debate within the parties about who has the best chance to win next November — and how much it should matter.

That fight is played out every four years as the two parties pick their presidential nominees. The party establishment — and many members of the media — tend to focus heavily on electability while the party’s activist base prizes ideological alignment.

“Electability usually doesn’t matter to Republicans,” said Alex Castellanos, a senior Republican strategist. “All of us consultants can cite limitless examples of campaigns wrecked on the shoals of that false light.”

The question now is whether the deep distaste for President Obama among Republicans — from the major donors to the grass-roots activists — will make voters follow their heads, not their hearts.

It’s a dynamic that played out seven years ago when Democrats were choosing someone to end the much-maligned tenure of President George W. Bush.

Former Vermont governor Howard Dean spoke to the passion of Democrats and looked like a surefire nominee as the calendar turned to 2004. But when it came time to choose, Dean was passed over for Sen. John Kerry (Mass.), a far-less-beloved candidate within the party base but someone with the résumé— most notably his time in Vietnam — that seemed to match up best with Bush’s. (In the New Hampshire primary, 33 percent of voters said nominating someone who could beat Bush was of paramount importance, and 56 percent of that bloc chose Kerry.)

Fast-forward to today, when an incumbent widely reviled by the party out of power is seeking a second term and the electability question is again a subject of fierce debate.

Polling seems to suggest that electability is taking a back seat to ideology. In a Washington Post-ABC News poll that concluded early this month, 73 percent of Republican respondents said it was more important to them to support a candidate they agreed with on the issues, while just 20 percent said a candidate’s chances of winning mattered most.

That sort of question, however, may be slightly misleading. The primary election may not come down to picking between a pure ideologue and someone ideologically flawed but electable.

“In primaries, message always matters most,” said Heath Thompson, a Republican media consultant who is not aligned with a candidate. “But in the absence of compelling distinctions and clear choices, electability grows in voter relevance. If they all basically seem the same, why not vote for the guy you think can win?”

The central question of the race, then, is whether former Massachusetts governor Mitt Romney, the most tested candidate in the GOP field and the one making the strongest appeal to electability, can blur the distinctions between himself, Texas Gov. Rick Perry and businessman Herman Cain.

“Considering what’s at stake — the possibility of four more years of President Barack Obama’s ruinously wrongheaded ideas — electability is a key factor,” Tim Pawlenty, a former presidential candidate who has endorsed Romney, wrote in a Politico op-ed last month. “We have to win.”

Romney has largely — and successfully — played down his main liability among conservatives: his signing of a health-care bill that was used as the model for the national law Obama enacted.

And his effort to keep the focus on electability has been helped by Perry’s struggles to explain his relatively moderate immigration views and Cain’s stumbles over whether abortion should be legal.

One thing that could work against Romney, however, is the mounting evidence of Obama’s political vulnerability heading into 2012.

“Electability is really beatability this year,” Republican pollster John McLaughlin said. “They all want to beat Barack Obama in the election, and right now they think all their major candidates can do that.”

Mark McKinnon, who made ads for Bush’s presidential bids, put it even more succinctly: “If the economy stays the same or gets worse, Republicans could nominate Ron Paul and win.”

And that may be bad news for Romney.