The list of consecutive winners is very small, especially since once upon a time people frowned on multiple winners altogether:
The MVP award is a rare treasure that many great players and Hall of Famers have never achieved. Only one is granted each year for each league, and the competition is so fierce that a number of criteria are used and their importance shifts from season to season based on sportswriters' bias and interpretation. Many players have had MVP-calibur seasons forgotten, because they fell in the shadow of someone else's magnificent season (Ted Williams hit .400 and lost to Joe DiMaggio, etc.). Doing it once is hard - doing it twice in a row is almost impossible.
[NL] 2008-2009 - Albert Pujols
[NL] 2001-2004 - Barry Bonds
[AL] 1993-1994 - Frank Thomas
[NL] 1992-1993 - Barry Bonds
[NL] 1982-1983 - Dale Murphy
[NL] 1980-1981 - Mike Schmidt
[NL] 1975-1976 - Joe Morgan
[AL] 1960-1961 - Roger Maris
[NL] 1958-1959 - Ernie Banks
[AL] 1956-1957 - Mickey Mantle
[AL] 1954-1955 - Yogi Berra
[AL] 1944-1945 - Hal Newhouser
[AL] 1932-1933 - Jimmie Foxx
But it does happen, and it happens at times when there isn't a lot of fierce competition. Right now, Braun has a lot of guys that are legitimate contenders, but for one reason or another they aren't in the competition this year. Matt Holliday is a perennial candidate, but is having an off-season (for him), with his OPS the lowest it's been since 2005. Joey Votto was going gangbusters in the first half of the season for first-place Cincinnati, and seemed to be a shoo-in for the award prior to his injury. Giancarlo Stanton, Jason Heyward, and Bryce Harper are still just kids, and they'll be fighting each other in the coming years to capture this award, but they're not quite there yet.
The only real competitor out there (unless we include pitchers Johnny Cueto and R.A. Dickey, which we should not) is Andrew McCutchen. If the Pirates make the playoffs then I think it's most likely that he will win the MVP simply because his accomplishments meant more than those of a candidate whose team did not. If they finish in the pack of also-rans with the Brewers however, especially with the Pirates continuing to slide, and could slip below the Brewers in the standings, then it becomes a personal numbers race.
When you face McCutchen and Braun head to head, one of the categories favors McCutchen - batting average. He is also ahead in offensive WAR, which isn't convincing because even though his numbers are high for a CF, he's actually got a -.2 dWAR as a CF, while Braun has a +.3 dWAR as a LF. In short, McCutchen's offense looks better compared to people at his position (Angel Pagan, Carlos Gomez), but his defense looks worse. Braun's offense looks less impressive because of the high average performance of everyone who plays left field (Matt Holliday, Melky Cabrera).
Then, there's the part that really matters, what I would call the situational buzz. Making Sports Center for hitting a walk-off home run, flying into the fence to take away a triple, extending a hitting streak to 20 games, and coming up with big hits off big pitchers in big cities are all things that can add to your perceived value. These create the perception of a player's value before people look at the final numbers. To date, Braun has been in the mind of many because of his home run total this season, and McCutchen has been a bit of a favorite because the Pirates extended their playoff hopes further this season than any in recent memory, and he's been fighting for a batting title (that he will receive sympathy for losing due to the steroid use of Melky Cabrera, which will be mentioned in the same paragraph as Ryan Braun's exoneration-and-continued-guilt by writers like Jeff Passan until the end of time).
And with all that glory and baggage the writers will then sit down with the numbers and make the call: Who has been the most valuable? If you had to make that judgment today, it would be close, depending on how much you value the distance between the Pirates (1.5 games out of the wild card) and the Brewers (6 games out) and the value of pure batting average (Braun leads McCutchen in virtually every other offensive category). The Pirates could still beat out the Cardinals for the playoffs.. and then again Braun could go 45 for 87 over the last 3+ weeks of the season and win the triple crown. Anything's possible.
And then there's the fact that Braun won it last year. Just because of that, some people will not vote for him. Others, we know, will not vote for him because Matt Kemp was statistically slightly more deserving than him last year but the Brewers were a winning team, and then the drug testing circus came to town to destroy Braun's image. So really, Braun has two people he's battling against for the title - McCutchen, and Himself, from last year. To win it not only does he need to beat McCutchen but he also needs to be perceived as statistically more improved vs. last year than the difference in the Pirates' and Brewers' success. It's not fair, but it's the system we've got.
And with that in mind, after much rambling, I provide two charts showing Braun this season in his race against McCutchen and the ghost of last season, in terms of Total Bases and aggregate WPA (win probability).
Total Bases, by game played over time
Aggregate WPA, by game played over time
As always, I'm an amateur at the statistical analysis thing and I do these things for my own amusement and share them to hear what other people think about the subject. All data from B-Ref.