IT WAS the open highway, not the broken road, that brought "American Idol's" Carrie Underwood and the rest of this year's contestants to MCI Center a few nights ago, and the same is true for Rascal Flatts, which headlines Friday at Nissan Pavilion.

Country music's hottest trio performed "Bless the Broken Road" with Underwood on the TV show's finale -- she'd sung the Rascal Flatts hit a couple of times along the way -- and that tender tale of heartbreaks and heartaches leading to true love may well have been the thing that put Underwood over the top. It certainly has been good to Rascal Flatts: The single spent six straight weeks at No. 1 on the country charts and helped "Feels Like Today" become only the second album by a country group to debut at No. 1 on Soundscan's Top 200 chart, the other being the Dixie Chicks' "Home." Like the Chicks, Rascal Flatts became only the second country group to top both Billboard's pop and country album charts.

Group founder and bassist Jay DeMarcus, who had joked that he hoped Rascal Flatts wouldn't get voted off the show, says of the "American Idol" experience: "It was a great thing for country music to be able to have that kind of exposure in the pop world. Typically 'American Idol' hasn't really embraced country music, [particularly scowling Simon Cowell] so for us to be asked to be on that show was a really great thing for all of us."

"Bless the Broken Road" had its own long road to travel. The song was written a decade ago by Bobby Boyd, Jeff Hanna and Marcus Hummon, who included a version on his 1995 "All In Good Time" album. But the song did nothing then and took its time showing up in Rascal Flatts' repertoire. (It was actually rejected for 2002's "Melt" album.) Now it has become a favorite at weddings and anniversaries.

"The truth of the matter is we'd heard that song several years ago and, for whatever reasons, just decided not to do it," DeMarcus says. "But after I got married and [guitarist] Joe Don [Rooney] got into a serious relationship, it sort of spoke to me differently, I guess, felt like something that was very much my life story. The melody was always great, and I knew that we would come up with a great arrangement if we decided to cut it. I think lyrically it just touched me in a different way when I found someone I wanted to spend the rest of my life with."

That would be former Miss Tennessee Allison Alderson. Rooney is engaged to 2005 Playboy Playmate of the Year Tiffany Fallon (the former Miss Georgia U.S.A. 2001 and December 2004 Playmate of the Month). Singer-heartthrob Gary LeVox is long married and has two young daughters, Brittany and Brooklyn.

"It's rough," DeMarcus says, admitting that dreams of romantic glory and commercial success were exactly that when he first moved to Nashville in 1992. "I imagined it, but sometimes the vision was hard to see through all the years of starving down there," DeMarcus quips. "But hard work does pay off, and once you set your mind to something, as long as you're willing to do whatever it takes to make it work, I do believe that your dreams will come true."

Another good result from the "American Idol" appearance: Kenneth "Babyface" Edmonds, who also performed on the finale, was so impressed with Rascal Flatts that he invited them to participate in a Bee Gees tribute album he's producing.

It's partly because of "American Idol"-styled ballads that appeal to the all-important female audience that Rascal Flatts became the hottest band in country music and last year's best-selling country group. Their eponymous 2000 debut sold 2 million copies with two No. 1 hits, "Prayin' for Daylight" and "I'm Movin' On," and "Melt" sold 2.5 million copies and produced another pair of No. 1s, "These Days" and "Mayberry."

LeVox's soulful lead vocals and the harmonies provided by DeMarcus and Rooney have had a lot to do with that success, as has Rooney's bare butt. The video for "I Melt," featuring a provocative love scene between Rooney and model Christina Auria, included a glimpse of Rooney's backside absent the usual tight pair of Wranglers. (There were some revealing shots of Auria as well.) The first video featuring nudity to air on country music cable channel CMT earned mixed reviews on the network's Web site, most viewers approving while some questioned the band's moral and religious convictions.

And, no, the group did not draw straws to decide who would be getting wider exposure.

"We absolutely, immediately handed that off to Joe Don," DeMarcus laughs. "He wasn't dating anybody at the time, I was engaged and Gary was married, so it fell to him."

When DeMarcus moved to Nashville, it was as half of a Christian pop duo called East to West with his Lee University (Cleveland, Tenn.) roommate Neal Coomer, but even as they recorded two albums, the city's dominant music strain was calling.

DeMarcus explains that they "started growing apart in terms of the musical direction we wanted to go -- I wanted to take the band a little more gritty than he did. We were such good friends that at the end of our second album, when we went in to do a third, I [told him] I wanted to write country music and be more of a songwriter in town, and we went our separate ways."

DeMarcus had grown up in Columbus, Ohio, sharing musical fantasies with second cousin LeVox (whose last name then was Vernon). LeVox had stayed there, working for the Ohio Department of Mental Retardation helping disabled people live independently, and DeMarcus didn't get him to Nashville until 1997.

"I hounded on him for about six months and finally talked him into it, thank God," DeMarcus says. "When I heard Gary sing, I knew I wanted to be involved somehow, writing and producing for him, but I didn't know we'd be in a band together."

At the time, DeMarcus was musical director for singer Chely Wright's band, with Rooney playing guitar. In Wright's downtime, DeMarcus and LeVox landed a regular gig at the Fiddle and Steel Guitar Bar, a well-known haunt on Nashville's Printer's Alley. One night, their guitarist couldn't make it, and they asked Rooney to sit in.

"And lo and behold, he just started singing harmony with us, and he knew all the songs we were doing," DeMarcus recalls. Rooney took the high part above LeVox's tenor -- DeMarcus had always disliked singing that part -- and by the end of the first song, they sensed they had something special. "We weren't really looking for anybody, but when we heard that blend . . .

"We've been singing together ever since."

And attracting critics without even having to bare their butts: When Rascal Flatts' debut came out, naysayers (mostly neo-traditionalists) riled by a trio of young, clean-cut guys serving up lush harmonies and treading the line between adult pop and contemporary country, dismissed them as a manufactured boy band, Nashville's answer to 'NSync and the Backstreet Boys.

According to DeMarcus, "It caught us by surprise when people started calling us a boy band because we'd always considered ourselves pretty serious musicians. Us being young and sort of clean-cut and not wearing cowboy hats sort of put us into that mold, and it was really disappointing at first because we wanted people to look beyond how we looked, to look at our music and see how serious we are about it.

"I think our live shows dispelled any misconceptions people had about us," he adds. "When you come see us live, you know we're anything but a boy band."

To prove their point, Rascal Flatts sought opening slots on tours by such stars as Alan Jackson, Toby Keith, Kenny Chesney and Brooks & Dunn, which allowed them to build a live following. It didn't take long, either: In 2002, the Country Music Association gave Rascal Flatts its Horizon Award, for the best up-and-coming talent and voted it the top vocal group in 2003 and 2004. In May, the trio won best vocal group honors at the Academy of Country Music Awards, joining Alabama as the only groups to win that award three years in a row.

They've also passed the 7 million mark in album sales, with "Feels Like Today" having sold almost 3 million copies since September. The album's latest single, "Fast Cars and Freedom," recently topped the country charts for four weeks.

Rascal Flatts' current "Here's to You" tour is named after the album's tribute to their fans, collectively known as the Dog Pound. The promotion-minded volunteers are reportedly the biggest street team in country music, and radio programmers, music writers and others often find themselves receiving Dog Pound-generated requests for airplay and coverage. They don't get paid but do get concert tickets, T-shirts, exclusive online chats (and occasional phone calls from band members) and other niceties.

"They do a great job for us," says DeMarcus, who co-wrote "Here's to You." "They're invaluable to our career, and they've been a big part of our success."

RASCAL FLATTS -- Appearing Friday at Nissan Pavilion with Blake Shelton.

Country hitmakers: Rascal Flatts' Jay DeMarcus, left, with Joe Don Rooney and Gary LeVox.