Amy's Path
The thing most people miss about Senator Klobuchar is that she never lets tactics overcome strategy and that she thinks things through all the time. While her path to the nomination is difficult it is no longer impossible and a lot better then people think. A lot of it has to do with how well she has run her campaign in a strategic sense.
So lets look at the state of the race today and just how Amy could win this thing.
From the start she always knew her path to the nomination runs through Iowa. Now that she has clearly moved within striking distance there possibilities open up and her strategic choices can have a big effect. First in Iowa she has emphasized lower level endorsements. What that has done is allowed her to have a much more local face to her campaign and to have a pool of experienced operatives/endorsers much closer to the regional and district caucuses. That is a huge advantage in the 15% math.
But more then that with the media forcing the Warren/Buttigieg tiff, she is now in a position to pick up a bunch of support. But so is Sanders. This actually makes sense because Warren and Buttigieg are fighting for the same voters right now.
An entirely plausible outcome right now is for Sanders to win by consolidating in the caucus Warren's more ideological support and for Klobuchar to pick up much of Warren's other support and much of the support Buttigieg has acquired from Warren. That could easily vault Amy into 2nd or 3rd. It would also be a huge shock to the perceptions of the national voting public. At this point Amy is in the best position to have a shockingly better outcome then any other candidate simply because she is not in the national conversation as much.
So on to NH with Amy surging and Warren/Buttigieg fighting for survival. Warren cannot attack it is simply not to her benefit at that point as she needs ideological crossover to beat Sanders, Buttigieg can do so but that hurts his all together now image and Amy has sowed the seeds very well of gender and experience. She has also been laying the groundwork in NH from the beginning. A Sanders win in Iowa will also hurt Biden if not as much. A nick in the inevitability will bring the lingering doubts back to the fore. Klobuchar has always looked to a direct comparison to Biden and she will get it. Again it is quite easy to see that after Iowa a Sanders win with a Biden/Klobuchar following is even more likely. That would be enough for the race to be really down to 3.
Nevada would then be a a test. But now gender politics would be clearly in play. An experienced woman against two older males. That is a hugely interesting dynamic that as the daughter of a union household could really play. I would expect Bernie and Joe to win thare but Amy right there in a 3 way race.
But now SC at this point Sanders is likely to come in with three wins and Biden would be in a must win. If he is in a must win he has already lost.
Which means that going into Super Tuesday we will have Sanders pounding on Bloomberg who is his perfect foil and Klobuchar consolidating the rest of the moderate wing and the electability "win track". At which point it is 2016 with Amy as Hillary without the EMails.