The Republican Party took a beating in November, dropping the presidential election and losing seats in both houses of Congress. It was a defeat so resounding that the party launched an internal "autopsy" report, and is now preparing to embark on a major rebranding effort.

Yet mere months removed from that drubbing, Republicans are already optimistic about their odds of retaking the Senate in next year's midterm elections. With a different political climate and a favorable electoral map in 2014, they feel that the six-seat gain they'd need to swing control of the Senate is realistically within reach.

The GOP's optimism received a boost today, with reports that Sen. Tim Johnson, the Democrat from South Dakota, will announce his retirement on Tuesday. The departure of Johnson, who won re-election handily in 2008, will only make it more difficult for Democrats to hold on in the increasingly Republican state. Indeed, National Republican Senatorial Committee spokesman Brad Dayspring boasted that South Dakota presents a "prime pick-up opportunity for Republicans regardless of whose name Democrats put on the ballot." South Dakota voters backed Mitt Romney by an 18-point margin in 2012.

Of the 35 seats up for grabs in 2014, 21 are held by Democrats, meaning the GOP can focus more on offense, while Democrats will have to expend more manpower and money on defense. As Nate Silver at The New York Times points out, most of the 21 seats Democrats must defend are in Republican-leaning states.

By Silver's early estimate, there are four toss-up races next year, all of them for seats currently held by vulnerable Democrats in states that went to Romney. Three other Democratic seats are considered to be "leaning" blue, while the open seat in West Virginia is given an 80 percent chance of switching hands.

By contrast, Silver's analysis pegs every Republican seat "safe" or a "likely" hold. Republican senators up for re-election are mostly in deep red states like Idaho, Alabama, Texas, and Wyoming, and their weakest incumbent is probably Maine's Susan Collins, whom Silver's forecast gives a 75 percent chance of winning re-election. Early polls have shown Collins with a commanding lead on potential challengers.

Here's Silver:

Summing up the possibilities across all 35 Senate races yields a net gain of four to five seats for Republicans, just short of the six they would need to win back the majority.

However, the margin of error on the calculation is very high at this early stage. Keep in mind that in each of the last four cycles, one party (Democrats in 2006, 2008 and 2012; Republicans in 2010) won the vast majority of the competitive races. [New York Times]

Complicating the picture for Democrats are the retirements of a handful of senators, including some in highly competitive states. In addition to Johnson, Sen. Jay Rockefeller's retirement in West Virginia after three decades in office makes that seat "the GOP's to lose," says Politico. And though outgoing Sen. Tom Harkin leaves Democrats with a slight edge in Iowa, conservative stalwart Rep. Steve King (R) could pose a strong threat if he gets in the race.

Also aiding the GOP is that 2014 is a midterm year which, as Politico notes, tends to produce an older, whiter electorate. High turnout buoyed down-ballot Democrats in 2008 and 2012, but the lack of a popular presidential nominee on the ticket could harm weaker candidates in 2014.

Add to all that the big GOP reboot — the party's new initiative to modernize its campaigns and adopt a more inclusive message — which, if successful, would help the party compete for a broader share of voters.

It's a long way to November 2014. Certainly, Republicans could nominate more self-defeating candidates like Todd Akin, or alienate their base with that much-ballyhooed rebranding effort. Any number of factors between now and Election Day could drastically alter the odds of a GOP takeover.

With the Tea Party revolt in full swing, Republicans gained six seats in the 2010 midterm shellacking. They likely won't have quite so favorable a political climate next year, but as the 2014 electoral map begins to take shape, they've already found some reasons to feel pretty good about their chances.