If President Obama is going to get anything else on his agenda done in the final two years of his presidency, he is going to need at least one chamber of Congress to remain in Democratic control.

Problem is, there is a decent chance that might not happen.

Democrats will be defending 21 Senate seats next November, compared to just 14 for Republicans. And seven of those elections will be taking place in states Mitt Romney won in 2012. Meanwhile, moderate Sen. Susan Collins, R-Maine, is the only Republican facing election in a state that Obama won.

Making matters worse for Democrats, incumbent senators are retiring in three out of the seven red state senate seats they will be defending.

Since Republicans will control 45 Senate seats going into 2014, they will only need to win six out of seven of the elections in states where Romney won in 2012. See the accompanying EXography U.S. map for additional information on the races in each of the seven states.

This is a tough hill to climb but many analysts say it is possible.

"They've got just under 50-50 odds," National Journal's managing editor for political coverage Josh Kraushaar tells the Washington Examiner, "By virtue of a favorable Senate playing field, Republicans can win back a majority simply by picking off seats in deeply-Republican states -- West Virginia, South Dakota, Arkansas, Alaska, Louisiana and Montana. It wouldn't even take a wave for them to succeed -- just credible candidates and well-run campaigns."

The Examiner's senior columnist Michael Barone agrees. Asked to give odds that Republicans will take the Senate in 2014, Barone says, "Less than 50 percent and much less than 50 percent if Republican primary voters pick weak candidates."

So far, Republicans have recruited strong candidates in three of the red state Senate seats they need (South Dakota, West Virginia, and Louisiana), and if Rep. Tom Cotton, R-Ark., decides to run, they should be two-thirds of the way to a majority.

South Dakota - Sen. Tim Johnson, D, won re-election with 62 percent of the vote in 2008, but he is retiring, and Romney won South Dakota easily, 58 percent to 40 percent, in 2012. Former Republican Gov. Mike Rounds has already announced his candidacy and every possible top Democratic candidate who was courted by the party, including Rep. Stephanie Herseth Sandlin, has declined to run.

West Virginia - Sen. Jay Rockefeller, D, won re-election with 64 percent of the vote in 2008, but he is retiring, and Romney won West Virginia easily, 62 percent to 36 percent, in 2012. Rep. Shelley Moore Capito, a moderate Republican, has already declared her intention to run for the seat, and she can transfer her $1 million war chest over from her House account.

Conservatives are unhappy with Capito's voting record, however, so she will have to win a primary fight before the general. Democrats, meanwhile, have no top tier candidates prepared to run.

Arkansas - Sen. Mark Pryor, D, won almost 80 percent of the vote in 2008 when he did not face any real opposition, but the state has trended strongly conservative since then and Republicans have a strong candidate already lined up.

Romney beat Obama 61 percent to 37 in the state and New York Mayor Michael Bloomberg is airing ads attacking Pryor for voting against gun control. Meanwhile, freshman Rep. Tom Cotton, R, is well-known and well-liked in the state and a recent head-to-head poll had Cotton beating Pryor 43 percent to 35 percent.

Alaska - Sen. Mark Begich, D, narrowly defeated incumbent Sen. Ted Stevens, 48 percent to 47 percent in 2008. Begich will have the advantage of incumbency now but the state also went for Romney handedly, 55 percent to 41 percent, in 2012. Fortunately for Democrats, Republicans haven't convinced anyone to declare their candidacy yet, but a recent poll showed that Anchorage Mayor Dan Sullivan would only trail Begich 47 percent to 41 percent, if he decided to run. Republican Lt. Gov. Mead Treadwell is also exploring a run.

Montana - Sen. Max Baucus, D, won re-election with 73 percent of the vote in 2008, but he is retiring, and Romney won Montana easily, 55 percent to 42 percent, in 2012. Gov. Brian Schweitzer, D, is widely popular but he has repeatedly said he does not want to come to Washington and had not declared his intention to run yet.

If he did run, he would be a slight frontrunner, with only former Gov. Marc Racicot beating him in a recent poll, 47 percent to 46 percent. Rep. Steve Daines would also be competitive against Schweitzer, trailing just 48 percent to 45 percent.

Louisiana - Sen. Mary Landrieu, D, won re-election in 2008 52 percent to 46 percent. But her approval rating is currently below 50 percent and Romney won Louisiana 58 percent to 41 percent. Rep. Bill Cassidy, R, has already said he will run against Landrieu and a recent poll showed him behind just five points, 46 percent to 41 percent. Like Capito, however, it looks like more conservative Republicans will force Cassidy to win a primary first.

North Carolina - Sen. Kay Hagan, D, defeated incumbent Sen. Elizabeth Dole, R, 53 percent to 44 percent in 2008. But President Obama was at the top of the ticket in 2008 and he won the state 49.7 percent to 49.4 percent. North Carolina has only become more conservative since then and Romney won the state 50 percent to 48 percent in 2012.

Hagan's job approval rating is far below 50 percent and Republicans are hoping state Labor Commissioner Cherie Berry will run against her. If she does, a recent poll shows Hagan would only trail Berry 46 percent to 41 percent. Republican state House Speaker Thom Tillis has already announced he will run.