For former U.S. Sen. Harris Wofford, it was instantaneous, "like lightning." For San Francisco therapist Michael Bader, it was a chill up the spine. For Republican activist Josh Lakey, it was more like a brain freeze, rendering him momentarily unable to speak.

Falling in love with a presidential candidate can do that to an otherwise reasonable person. Forget the policy papers on tax credits or NAFTA, forget the gaffes about bitterness or Bosnia: the cheeks burn, the heart pounds, the stomach churns when the beloved takes the podium to troll for votes.

In this most electric of election seasons, Sen. Barack Obama gets the prize for making the most women swoon at his rallies. At one event before the Maryland primary, he answered the "I love you Obama!" cries from the crowd of 16,000 with a cozy: "I love you back."

Other women have been known to choke up when Sen. Hillary Rodham Clinton -- the first truly credible female presidential candidate -- walks into an arena, and still others are struck speechless when Sen. John McCain begins waxing rhapsodic about tax cuts.

But the heated, ardent reaction Mr. Obama inspires in his followers, whom Mrs. Clinton mocked as a "movement" and whom even he half-joked about being "delusional" -- strikes some as relatively rare in modern politics.

"It was love at first sight for me," said Mr. Wofford, 82, of his initial encounter with Mr. Obama, 46, in 2004, when he heard the senator's now-famous speech at the Democratic National Convention. Mr. Obama, he said, has that quality that Franklin D. Roosevelt had. "He'd be a teaching president, like FDR, someone who knows how to reason with people, to talk things through with them.

"I knew that this man was someone I'd been waiting for ever since Jack and Bobby [Kennedy], and I still believe that."

Charles Gerow, a longtime GOP operative and public relations consultant based in Harrisburg, has an immediate reaction when asked if he was ever "in love" with Ronald Reagan.

"Sure," he says of the man for whom he performed campaign and advance work right up to the 40th president's funeral. "Well, maybe I'd better clarify that. I was certainly enthralled with Ronald Reagan, and I think he captured the imagination and the soul of America. He was the eternal optimist, and people loved that, even young people. He made a whole generation of high schoolers fall in love with him."

At a private reception in the Philadelphia suburbs two weeks ago, Mr. Wofford noted, Caroline Kennedy, daughter of the late president, expressed wonder at a poll listing her father and Mr. Reagan as America's two greatest presidents.

"But then she said, upon further reflection, she wasn't really surprised because both men projected the same kind of idealism, even if their policies were very different," he added.

Falling in love with a candidate is not solely the province of the weird or maladjusted, nor is it particular to one party or another, say political scientists who specialize in voter behavior.

"It's a very real psychological and behavioral phenomenon in politics," said Rebecca Hannagan, an assistant professor of political science at Northern Illinois University. "In terms of what we understand about affective attachment and emotional cues, the attachments people can have to particular political candidates can be overwhelmingly powerful and incredibly effective."

Except that they may not know it.

"There are a lot of things that guide our political attitude formation that aren't consciously apparent to us," she added. "But in studies, people say all the time, 'I voted for him, he seemed like a nice person,' or something along those lines."

The fuss over Obama is unusual, she said.

"It's more than charisma, even. It would make for an interesting study, what happens to our brains when we come into contact with these people. A number of Republicans have said they didn't want to like Obama, and, frankly, Mike Huckabee has had a similar effect on the other side."

Although the physiological underpinnings of political "love" are still not clearly understood, there's wide agreement on its power. "I don't think there is any doubt that most people choose their elected leaders on the basis of nonverbal cues and intuition more than rational evaluation of a series of issue positions," said Tony May, senior vice president for communications at Harrisburg-based Triad Strategies.

"People become devoted to sports teams for reasons that have nothing to do with on-the-field performance," said Mr. May, who worked for years in state Democratic politics. "People become enamored with showboats like Terrell Owens because it is as much -- if not more -- about personality than it is about performance. Apparently ... people still love George Bush and are appalled at the suggestion that he is about to go down in history as one of the worst presidents of all time. What I see as the 'Bush smirk' they see as his 'wry smile.' Go figure."

Kathleen Hall Jamieson believes the role of nonverbal cues, at least by themselves, is overstated -- as is the whole notion that voters can actually fall in love with a candidate.

"Love is the wrong way to describe a relationship with someone you're going to elect," said Dr. Jamieson, co-author of a new book, "Presidents Creating the Presidency," and a communications professor at the University of Pennsylvania's Annenberg Public Policy Center.

Three things have to happen to create an intimate connection between candidate and voter, she said.

"There has to be a compelling message. It has to be tied to a reinforcing biography. Then there must be a sense that this is an authentic person. You have to have all three -- you can't take them apart or you won't get the same effect."

Witness the difference between Sens. Robert F. Kennedy and Eugene McCarthy in 1968, she said. While Mr. McCarthy inspired fierce loyalty, he was cool and professorial, while there was almost a kinetic connection between the shirt-sleeved, rumpled Mr. Kennedy and his audiences, she said.

Mr. Wofford, who traveled with Bobby Kennedy during the 1968 primary season in Northern California, remembered that Mr. Kennedy had scratches on his arms from people trying to touch him.

"It was incredible," he remembered. "People just wanted to be near him. He had developed this passion about civil rights, the poor, about foreign policy, that I hadn't seen before, and voters really felt it. I certainly felt it."

So did Mr. Bader, who, like a lover recalling every detail of a tryst, remembered his one encounter with Bobby Kennedy in San Jose, Calif., 40 years ago.

"It was late afternoon on a hot, very windy Sunday, and it was a rally organized by the farm workers," he said. "He was an hour or two late, but when he came up on stage, it was like an electric current went through the crowd. He wasn't the [Hubert] Humphrey 'Happy Warrior.' He was young and virile, of course, but also someone whose face conveyed some pain, and some type of poignant compassion for the poor. I remember it made me feel like I was part of something bigger than myself."

When Mr. Bader watched Mr. Obama's speech from South Carolina, he felt the same way -- "chills up my spine," he said.

But rarely is such a reaction universal. "The voter has to be receptive to the candidate's message," said Dr. Jamieson. After all, not everyone loved Jack or Bobby Kennedy, or not everyone, for that matter, loves Barack Obama.

"Ronald Reagan had that effect on everyone but liberal Democrats," she added. "When the message runs against your own ideology you short-circuit the identification."

Which is why Josh Lakey will probably never be an Obama fan.

John McCain, though, is another matter.

Whatever it is, it made the 26-year-old East McKeesport native freeze up when he was presented with an opportunity earlier this week to meet his hero, after a fund-raiser at the Omni William Penn Downtown.

"[Mr. McCain] walked out the door, and I froze for a second and thought, 'My God, I'm looking at a man who has done more in 71 years and sacrificed more for his country than most people could ever imagine.'"

Still speechless, he handed the Arizona senator his camera.

"He kind of looked at me funny and said, very gently, 'Maybe you should give the camera to someone else if you want me to be in the picture with you.'"

Mr. Lakey did, and today he has a photo he will always treasure of the man he -- what?

"I don't know," said Mr. Lakey, president of Young Republicans of Allegheny County. "I want to say infatuated -- oh, I don't know what the right word is.

"I guess when you spend a lot of time following or working on a campaign, you start feeling connected to the candidate and you invest a lot of time thinking about the candidate and worrying about the candidate."

Why, it's almost like being in love.