U.S. Rep. Kyrsten Sinema (D-Ariz.) in August 2013. (Matt York/AP)

After mounting speculation that she might switch districts, Rep. Kyrsten Sinema (D-Ariz.) announced Thursday that she will stay put and run for reelection in the 9th district, a boon to House Democrats with an eye on holding her competitive district.

"I am flattered that some of my old neighbors and friends asked me to consider running for Congress in District 7. But I love my job representing the people of the 9th district and there is so much more to be done on behalf of the middle class," she said in a statement on her Facebook page.

After Rep. Ed Pastor (D-Ariz.) announced his retirement last month, Sinema reportedly thought about switching to his district to run for the open seat. It's much safer Democratic terrain, where President Obama won 72 percent of the vote. In Sinema's current district, Obama won 51 percent. And the congresswoman faces a potentially competitive race there.

But Sinema said her 2014 campaign in the 9th district was already up and running.

"My reelection campaign has already started and we look forward to talking about the work we have done and the work we still have to do to ensure that every Arizonan has a shot at the American Dream," she said.

National Republican Congressional Committee spokesman Matt Gorman said: "That fact that Congresswoman Sinema even considered abandoning her constituents for a safer district proves that she knows she’s completely out-of-touch with the people she claims to represent."