Representative Ann Kirkpatrick speaks during a news conference at the House Triangle in Washington, D.C. on May 7, 2014 and Senator John McCain speaks at the U.S. Capitol, Feb. 10, 2015. CQ Roll Call/Getty Images

As popular Arizona Republican Sen. John McCain seeks a sixth term in the U.S. Senate, a potential Democratic opponent today emerged after Rep. Ann Kirkpatrick, a three-term lawmaker from Flagstaff, entered the race.

"In Arizona we tell it straight, so let’s get right to it,” Kirkpatrick said in a campaign video announcement. “I’m announcing my candidacy for the United States Senate. I love this state."

McCain, who would turn 80 before Election Day, is unlikely to draw any Republican House members into a primary -- but facing off against Kirkpatrick, who is well-funded, could possibly prove to be a tough race for the former Republican presidential nominee.

Later in the video announcement, Kirkpatrick, 65, addressed the elephant in the room.

"I respect John McCain’s service to our nation. I just believe our state’s changing,” she said. “Arizonans should have a real choice who they send to the United States Senate."

McCain communications director Brian Rogers said McCain "welcomes" Kirkpatrick to the race and "looks forward to running a vigorous campaign no matter who the Democratic nominee is."

Kirkpatrick’s annoucement gives Democrats their first declared candidate in the race.

“Since 2008 John McCain has supported plans to gut Medicare and Social Security, repeatedly voted to shut down the government, and been the bitter, angry face of Washington's partisan dysfunction,” Justin Barasky, communications director for the Democratic Senatorial Campaign Committee, said. “If John McCain wins the Arizona GOP nomination, Democrats are committed to running a strong campaign against him.”

Republicans, on the other hand, are bullish on McCain's prospects.

"Ann Kirkpatrick has been part of the problem in Washington and Arizonans are paying the price," Andrea Bozek, communications director for the National Republican Senatorial Committee, said. "She doesn’t believe we should ‘second guess' President Obama which is why she supported ObamaCare, his trillion dollar stimulus that created jobs in China and cuts to Medicare. There is no question Ann Kirkpatrick has made life worse for Arizona families.”

As for Arizona's first congressional district that Kirkpatrick leaves open? It is certain to be one of the most hotly contested House races of the 2016 cycle.

“No matter how they try to spin it, this is a huge setback for House Democrats," Zach Hunter, a spokesman for the National Republican Congressional Committee, said. "The 1st District is a prime pickup opportunity for Republicans in 2016.”

But Democrats believe that a presidential election year will increase voter turnout to their benefit.

“Democrats know what it takes to win in this district, as we have proven repeatedly,” Matt Thornton of the DCCC said. “We are confident we will have a strong candidate who will keep this district in the Democratic column in 2016.”

News of Kirkpatrick’s Senate candidacy was first reported by Roll Call.