The Drum Major Institute evaluated the whole Senate based on 8 key votes to support the middle class, from protecting social security to fair trade to Medicare drug protections to the minimum wage:

Only 9% of the Senate (all Democrats) were awarded the highest grade of "A" for supporting the middle class on all 8 issues:

Hillary was one of those 9 Senators who got an "A" for consistently supporting the middle class (along with Boxer, Kennedy, Kerry, Sarbanes, Corzine, Lautenberg, Leahy, and Feingold). For comparison, both McCain and Hagel got an "F".
http://www.drummajorinstitute.com/congress/outerenvelop... Hillary is way too DLC for my taste, but she's hardly "the most right wing" while Biden and Richardson remain in the race.
If you need some good reasons to support Hillary in the general election if we do not succeed in nominating a more progressive candidate, why don't you start with the 8 issues and key votes identified by the Drum Major Institute.