Republicans began the 2012 election cycle expecting to win the four seats needed for Senate control. Instead, they ended up down two seats, largely because of poor recruitment and candidate gaffes.

For Democrats, they held off a GOP take-over attempt of the upper chamber for the second cycle in a row. This year, they won all but one of the most-tightly contested Senate races, including in three states most expected them to lose: Indiana, Missouri and North Dakota. They had twice as many seats to defend this cycle, and a number were in red states.

Republicans, meanwhile, won only one new seat, in ruby red Nebraska, and lost three others in Massachusetts, Maine and Indiana. They did retain seats in Nevada and Arizona, where Democrats had surged but failed to defeat Sen. Dean HellerDean Arthur HellerRepublican drops Senate primary challenge to Heller after Trump's urging Three states where Dems can pick up Senate seats GOP senator: Justice Kennedy is going to retire this summer MORE (R-Nev.) and incoming-Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeSenate GOP: Legislation to protect Mueller not needed Trump prepared to hit China with B in annual tariffs: report White House, Democrats reject competing DACA offers MORE (R-Ariz.)

National Republican Senatorial Committee Chairman John CornynJohn CornynTrump adds to legal team after attacks on Mueller Senate tees up Yemen vote for Tuesday Senate GOP: Legislation to protect Mueller not needed MORE (R-Texas), who for the second time failed to capture a majority for his party, was the first to admit the GOP's problems.

"It's clear that with our losses in the presidential race, and a number of key Senate races, we have a period of reflection and recalibration ahead for the Republican Party," Cornyn said in a statement on Tuesday night. "While some will want to blame one wing of the party over the other, the reality is candidates from all corners of our GOP lost tonight. Clearly we have work to do in the weeks and months ahead."

Cornyn predicted back in August 2010 that Republicans would win control of the Senate by 2012. Instead they fell five seats short.

No single event or trend led to the Democrats' huge night.

But their chances were boosted by gaffes from Republican nominees in Missouri and Indiana. Rep. Todd Akin (R-Mo.) became the subject of national attention when he made his controversial comments on "legitimate rape." Republicans tried to get him withdraw from the contest but he prevailed, despite the NRSC lack of public support. In Indiana, Republican Richard Mourdock came under fire for his controversial explanation of why he didn't believe in abortion in cases of rape: "Even when life begins in that horrible situation of rape that it is something God intended to happen," he said.

The failure of Akin and Mourdock led to comparisons of the 2010 busts from GOP candidates Sharron Angle in Nevada, Christine O'Donnell in Delaware and Ken Buck in Colorado, whose primary wins likely cost the GOP seats they expected to pick up. Akin won a competitive GOP Senate primary and Mourdock defeated longtime Sen. Dick Lugar in their primary — two wins which boosted Democratic hopes of winning in those states. If all five of those races had gone to the Republicans they would be at 50-50 parity in the Senate.

Cornyn and the GOP also failed to recruit strong candidates in a number of competitive swing states, most notably in Florida and Ohio, where Rep. Connie Mack's (R-Fla.) campaign got caught up in a public battle with a prominent Florida political reporter and Republican Josh Mandel never caught fire against Sen. Sherrod BrownSherrod Campbell BrownDemocratic senator: People don’t know what’s going on between Trump and Putin Power struggle threatens to sink bank legislation Pension committee must deliver on retirement promise MORE (D-Ohio).

The GOP also didn't offer serious challenges in the slightly Democratic-leaning states of Michigan and Minnesota.

Mitt Romney's decision not to seriously contest Michigan and Pennsylvania also made it more difficult for Republicans to win there.

And Democrats proved to have better candidates in open seats in North Dakota, Virginia and Wisconsin. Democrat Heidi HeitkampMary (Heidi) Kathryn HeitkampBiden: Trump ‘dumbs down’ American values Power struggle threatens to sink bank legislation Overnight Finance: House threatens to freeze Senate Dodd-Frank rollback | New Russia sanctions | Trump vs. Trudeau on trade | Court tosses Obama financial adviser rule MORE ran a smart, tough campaign in North Dakota and she won a close race there. Democrats Tim KaineTimothy (Tim) Michael KaineBill to bolster gun background checks gains enough support to break filibuster Senators demand cyber deterrence strategy from Trump Two-year defense spending smooths the way to a ready military MORE in Virginia and Rep. Tammy BaldwinTammy Suzanne BaldwinFlood of legislative candidates points to enthusiasm in both parties Koch-backed group puts .6M into ads hitting Wis. senator over VA scandal GOP candidate’s brother donates to campaign of Dem he hopes to unseat MORE in Wisconsin also prevailed in races considered toss-ups.

Meanwhile, several strong Republican candidates where hurt by their party's poor image in their states. One of the toughest losses for the GOP was in Massachusetts, where freshman Sen. Scott Brown (R-Mass.) ran away from his party but still lost to Democrat Elizabeth WarrenElizabeth Ann WarrenFix the flaw in financial self-regulation Power struggle threatens to sink bank legislation Feinstein faces new pressure from left over CIA nominee MORE. Republicans Linda McMahon in Connecticut, Heather Wilson in New Mexico and Linda Lingle in Hawaii also touted their independence but ultimately lost. President Obama's win in those states was some help, offering Democrats slight coattails.

Ultimately, the 2012 setbacks complicate GOP chances of winning control of the Senate in 2014. Democrats will once again be playing defense in many more states, having to defend seats in six red states: Alaska, Arkansas, Louisiana, Montana, South Dakota and West Virginia.

They also have seats up in the swing states of Iowa, Michigan, Minnesota, New Mexico, North Carolina and Virginia, while Republicans' only possible tough seat is in Maine, but if Sen. Susan CollinsSusan Margaret CollinsHouse leaves out ObamaCare fix from must-pass funding bill Senate considers vote to add ObamaCare fix to spending bill ObamaCare deal in danger of falling out of spending measure over abortion fight MORE (R-Maine) runs for reelection she's likely in good shape.

Republicans now need to net six seats to put Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSenate tees up Yemen vote for Tuesday Senate confirms Trump's border chief House leaves out ObamaCare fix from must-pass funding bill MORE into the majority leader's office  — a much more difficult task.