I think from the teams mentioned here Bayer Leverkussen has the true potential to contend for the title until the end of the Bundesliga,they seem compact,they won against Leipzig and they drew at Bayern Munchen home so they are really in a great form.They are also consistent which is a different feature compared to Leipzig for example as even Leipzig has been contending for the title in these last couple of years but clearly lacking consistency.
Dortmund is a great team but that has shown big fragility when they need the most to win the games,remember last game of last season where they lost the title at their home soil.
Well you're right cause their performance is very brilliant this season and they're one of the teams that's given Bayern Munich a tough time this season, they don't have a squad full of top class players, but they understand themselves and have good team spirit coupled with a young and vibrant coach with lots of ambitions, though Leipzig are also one of the strong contenders for the league and have given Bayern a tough time even defeated them in a final, but Leverkusen are better than them in consistency and would finish above them as well.
Dortmund didn't show great concern like they did last season , though they're still unbeaten in the league which means if they had put more effort from the beginning of the league, they would had been ín the position of Leverkusen on the standings, well they're on the right track and currently in top 4.
There is no doubt thats the strategy used by Xabi Alonso has really made a bigs difference to Leverkusen since Xabi Alonso joined the club, making Real Madrid want to recruit him to replace Carlo Ancelotti, but it look like Leverkusen will not let that happen.
The coach has made Leverkusen appear so impressive in the past two season thats Leverkusen took quick steps to sign Xabi Alonso long term.
If Leverkusen is able to continue to maintain its consistency until the end of the season, Leverkusen desire to winner the Bundesliga title this season will soon come true and Xabi Alonso should be appreciated for his successfull in coaching Leverkusen.
it looks like Dortmund not so much about winner a title in the Bundesliga because he is more concerned with his business of being able to sell the talented players at the club. With Dortmund current performance, Dortmund is good enough for Dortmund to be in the top 4 and possibly in the next season transfer market next winter, Dortmund will sell its talented players again, and like the rumors I heard, Bayern Munich want Dortmund goalkeeper its Gregor Kobel. If Bayern Munich is able to pay a high price for this players, it is not impossible thats Dortmund will give him to Dortmund arch rival in the Bundesliga..