Chris Bowers suggests 8 rules for Progressives when politicking within the Democratic Party:

1. The Democratic Party is the primary vessel of the progressive coalition. It is impossible to enact real change without an electoral apparatus within your movement. In a two-party system, it is thus necessary to adopt one of the two parties as the electoral vessel of your coalition. 2. Within the coalition, intra-party democracy must always be adhered to. All party nominees must be determined by an elective primary open to all registered members of the party in the relevant district. The winner of the primary must always be supported by all members of the party apparatus, and all rank and file members should vote for the nominee (especially those who voted in the primary). 3. Party elections should be fair and open to all members of the party, and no one should ever be forced or muscled off of a ballot for a party office or nomination for public office. 4. There are no litmus tests to join the coalition. No one has to read or sign off on any document stating support for a particular policy. If someone wants to join, registering as a Democrat should be the only requirement. 5. Under no circumstances should any member of the party apparatus support any member of any opposing coalition, (in other words, any other political party). 6. Outside of issues relating to corruption, Democrats must never criticize each other in the same manner that Republicans criticize Democrats. 7. No Democrat should ever publicly call any Democrat unelectable, or publicly rank candidates based on perceived electability. 8. Don't expect the party to change on it's own. Be prepared and willing to change it yourself.

Working outside this framework of rules, says Chris, limits a Progressive's ability to drive change in the system.