Unless Ron Paul somehow wins the nomination, it looks as if a vote for the Republican presidential candidate this fall will be a vote for war with Iran.

No other conclusion can be drawn from parsing the candidates’ public remarks. Paul, of course, is basically an isolationist who believes it is none of our business if Iran wants to build nuclear weapons. He questions even the use of sanctions, such as those now in force. But Paul has about as much chance of winning the GOP nomination as I do.Mitt Romney, Rick Santorum and Newt Gingrich have all sought to portrayPresident Obama as weak on national security — a traditional Republican line of attack. They have tried to accuse Obama of being insufficiently committed to Israel’s defense. In the process, they’ve made bellicose pledges about Iran that almost surely would lead straight to conflict.

Santorum’s apocalyptic rhetoric about Iran practically takes for granted an imminent clash. Gingrich would essentially abdicate the decision to Israeli leaders, giving them the green light for an attack whenever they choose.

Romney, the likely nominee, has been somewhat more circumspect — and less forthright. He published an op-ed in The Post this week blasting Obama’s foreign policy as “feckless” and promising that, under a Romney administration, things would be different. He then went on to outline the steps he would take in dealing with Iran — most of which turn out to be steps Obama has already taken.

“I will press for ever-tightening sanctions.” Check. “I will speak out on behalf of the cause of democracy in Iran and support Iranian dissidents.” Check. “I will make clear that America’s commitment to Israel’s security and survival is absolute.” Check. “I will buttress my diplomacy with a military option.” Check.

Romney’s only new initiatives would be to make Jerusalem the destination of his first foreign trip and to deploy an additional aircraft carrier group in the region. I imagine the intent would be to show Iranian leaders that they are isolated and under siege, but I think they get that already.

In a speech to the American Israel Public Affairs Committee — a pro-Israel lobbying group — Romney was much more specific in establishing his bottom line: “We must not allow Iran to have the bomb or the capacity to make a bomb.” It is difficult to imagine how this statement can lead anywhere but to war.

U.S. policy under Obama — and previous administrations — has been that it is “unacceptable” for Iran to have nuclear weapons. The clear implication is that, while military force is an option that could be employed at any time, including the present, forcewill be employed if Iran tries to make a bomb.

To say that Iran must never have “the capacity to make a bomb,” as Romney does, is to draw a line that has already been crossed.

Does capacity mean having the fuel for a bomb? Iran knows how to produce the enriched uranium that would be used in a bomb, and while U.S. air power alone — unsupported by ground troops — could destroy or damage most of the enrichment facilities we know about, the Iranians could have the program back up and running within a few years.

Does capacity mean the expertise necessary to construct a bomb that would actually explode? If so, will Romney order an attack whenever intelligence agencies report that a librarian at some Iranian university has ordered a textbook in advanced metallurgy from Amazon.com?

The truth is that every nation with sufficient wealth and scientific infrastructure has the capacity to build a bomb if it really wants to. An attack is likely to increase the Iranian regime’s resolve, not lessen it. Bombing Iran every few years is not a realistic option and in any event would not be effective in the long run; when the Iranians rebuild their facilities, they will surely do a better job of hiding and bunkering them.

The United States and its allies should seek to eliminate the Iranian government’s will to make a bomb, not its capacity. I hope Romney realizes that, while sanctions and diplomacy may not be working as well as we’d like, they’re the best tools we have — and that an attack at this point gets us nowhere. But if he believes his own rhetoric, this election may be about more than the economy. It may be about war and peace.

eugenerobinson@washpost.com