By Adam Levy, Wade Payson-Denney and Ashley Killough, CNN

(CNN) -- Two major retirement announcements this week could signal that control of the House of Representatives is up for grabs next year.

As moderate Republican members Dave Reichert and Charlie Dent prepare to leave Congress, conservatives want stronger allies in their seats, while Democrats see an opportunity to flip them.

Democrats need to pick up 24 seats to retake the majority from Republicans, who've maintained control of the House since 2011.

The campaign committees on both sides are eying the 23 Republicans defending districts that Hillary Clinton won, and the 12 held by Democrats in districts that President Donald Trump won as vulnerable seats to flip.

While midterm elections are historically tough for the party of the President in power, it's too early to tell how things will unfold next year.

Here is a rundown of representatives who have so far announced that they plan to retire or run for another office.

Retiring

Rep. Sam Johnson (R, TX-3) announced via press release on 1/6/17

Rep. Lynn Jenkins (R, KS-2); announced via Facebook post on 1/25/17

Rep. Ileana Ros-Lehtinen (R, FL-27); told the Miami Herald on 4/30/17

Rep. John J. Duncan Jr. (R, TN-2); told local media on 7/31/17

Rep. Niki Tsongas (D, MA-3); announced via press release on 8/9/17

Rep. Dave Reichert (R, WA-9) announced via press release on 9/6/17

Rep. Charlie Dent (R, PA-15) announced via press release on 9/7/17

Rep. Dave Trott (R, MI-11), announced via press release on 9/11/17

Rep. Carol Shea-Porter (D, NH-1), announced via statement on 10/6/17

Rep. Jeb Hensarling (R, TX-5), announced via email to supporters on 10/31/2017

Rep. Lamar Smith (R, TX-21), announced via statement on 11/2/2017

Rep. Frank LoBiondo (R, NJ-2), announced via statement on 11/7/2017

Rep. Ted Poe (R, TX-2), announced via Facebook on 11/7/17

Resigned or resigning

Rep. Jason Chaffetz (R, UT-3); left House on 6/30/17 to become a Fox News contributor (Special election November 7)

Rep. Tim Murphy (R, PA-18), announced via statement on 10/4/17, will leave on 10/21/17 (Special election TBA)

Rep. Pat Tiberi (R, OH-12), announced via statement on 10/19/17, will leave "by January 31, 2018" (Special election TBA)

Running for other office

President

Rep. John Delaney (D, MD-6); announced via The Washington Post on 7/31/17

Governor

Rep. Kristi Noem (R, SD-AL); announced via YouTube on 11/14/16

Rep. Michelle Lujan Grisham (D, NM-1); announced via Youtube on 12/13/16

Rep. James Renacci (R, OH-16); announced via campaign video on 3/20/17

Rep. Tim Walz (D, MN-1); announce via local newspaper on 3/27/17

Rep. Raul Labrador (R, ID-1); announced via local media on 5/9/17

Rep. Jared Polis (D, CO-2); told Denver Post on 6/11/17

Rep. Steve Pearce (R, NM-2); told Albuquerque Journal on 7/10/17

Rep. Diane Black (R, TN-6); announced via Facebook post on 8/2/17

Rep. Colleen Hanabusa (D, HI-1); announced via release on 9/1/17

Senate

Rep. Beto O'Rourke (D, TX-16); announced in El Paso on 3/31/17

Rep. Evan Jenkins (R, WV-3); announced via web video on 5/8/17

Rep. Jacky Rosen (D, NV-3); announce via The Nevada Independent on 7/5/17

Rep. Luke Messer (R, IN-6); announced via tweet on 7/26/17

Rep. Todd Rokita (R, IN-4); announced via YouTube on 8/9/17

Rep. Lou Barletta (R, PA-11); announced via campaign video on 8/29/17

Rep. Kyrsten Sinema (D, AZ-9) announced via YouTube video on 9/28/17

Rep. Marsha Blackburn (R, TN-7), announced via online video 10/5/17