The Vocal Group of the Year nominees at the 2015 ACM Awards include some of the biggest acts in country music. With hits like "Bartender," "Day Drinkin'" and "Chainsaw" heating up the radio and headlining tours trekking across the country, these five vocal groups are all deserving of a trophy.

With nine No. 1 hits under their belts, Lady Antebellum are a group that knows success. They released 747 last year; popular singles from the disc include "Bartender," "Freestyle" and the recently released "Long Stretch of Love," all of which showcase a funky, more celebratory style.

"One thing we've learned — and it’s been proven to us over the past couple of years — is that when we do take chances, the fans have responded really well,” Charles Kelley says. “We’d fallen into a very similar style, that mid-tempo thing with some melancholy to it. With this record, we wanted to try different things and make it really in your face."

The trio's Wheels Up 2015 Tour will kick off its North American leg on May 1.

Founded in 1998, Little Big Town are a four-part group that's not easily forgotten. Their sixth studio album, Pain Killer, hit the shelves on Oct. 21, but before that, LBT got some life-changing news: They were invited by Reba McEntire to join the Grand Ole Opry (of course they accepted). The Grammy-nominated group recently decided to extend their Pain Killer Tour because they were having so much fun, and they won Vocal Group of the Year at the 2014 CMA Awards.

Rascal Flatts are seasoned legends in country music. They have 15 No. 1 singles, almost 23 million albums sold and 30 million digital downloads. They're popular enough to have their own Las Vegas residency, and their Riot Tour 2015 kicks off in May. The Flatts' newest record, Rewind, showed the group taking more risks in their music while still staying true to the impeccable harmonies that put them on the map.

"We felt like it was important for us this time, after we got together and talked, to sit down and challenge ourselves musically," band member Jay DeMarcus explains.

Fresh off a 2015 Grammy Awards win for Best Country Duo / Group Performance, sibling trio the Band Perry are on fire. With their record Pioneer featuring hits like "Done," "Chainsaw," "Don't Let Me Be Lonely" and more, TBP have garnered a whole lot of attention for their fresh sound, innovative harmonies and gripping performances. Their upcoming record is shaping up to be another fan favorite, with unexpected collaborations garnering a lot of hype -- as they should.

Finally, the Atlanta-based Zac Brown Band have dropped three studio albums, each of which sold at least one million copies, and their 2013 EP, The Grohl Sessions, Vol. 1, with Foo Fighters frontman Dave Grohl, flew into the hands of eager fans. Their fourth studio album, Jekyll + Hyde -- featuring their newest single "Homegrown," collaborations with Chris Cornell and Sara Bareilles and a song written by Jason Isbell -- will be released at the end of April. The band is also gearing up for a 2015 tour, which is set to run from May through September.

"We’re all continuing to grow up and get better as musicians, and the chemistry as a band continues to deepen,” Brown explains. "Our boundaries have dissolved, and we’re going to still do things that are somewhat familiar that people like, but we’re also going to stretch out and take chances beyond what we've done before. Some people are going to be really surprised."

Who do you think will take home Vocal Group of the Year the 2015 ACM Awards? Vote as often as once an hour in the poll below until the end of the day on April 15. We’ll tabulate the results and use them for our 2015 ACM Awards winners predictions the week before the show.

The 2015 ACM Awards will air live from AT&T Stadium in Arlington, Texas, on April 19 at 8PM ET on CBS.