Only if he starts winning big in delegate-rich states. Barely eking out a win doesn't do him any favors. Since Democrats award pledged delegates proportionately (not by winner takes all), he and Clinton will just split the delegates, which will make it harder for him to catch up. On Monday, he had a 200 delegate deficit, and now it's up to 218.
No doubt that barely losing Michigan was a minor setback for Clinton, but she still came out the night's winner, thanks to her major win in Mississippi. At the end of the day, she got 87 delegates to his 69. She actually widened her lead by 18 delegates and now has 762 pledged delegates to his 544.
Next week (when delegate-rich Florida, Illinois, North Carolina, and Ohio vote) should give us a clearer picture whether Sanders' MI win was a fluke and it's the beginning of the end, or if it gave him any momentum.
Salve, Regina, Mater misericordiae
Vita, dulcedo, et spes nostra
Salve, Salve Regina
Ad te clamamus exsules filii Eva
Ad te suspiramus, gementes et flentes
O clemens O pia