In your opinion the last time Democrats "changed", ahem, had a serious disagreement with "The Party" was?
I'm recalling the early Clinton years and Hillary-care.
They've disagree'd with each other where the Conservative Dems don't go along with the more Liberal Dems. The Democrats have a big tent.
The healthcare law was a prime example. If it weren't for the more Conservative Dems like Mary Landrieu, Ben Nelson, Joe Lieberman, etc. there would of been a public option and or Medicare for all. During the debate over extending the Bush tax cuts some of the more Conservative Democrats supported rolling back the cuts on higher income tax levels than others. Instead of income levels of $250,000/year, they settled for $450,000/year.
These are just a couple of examples. Until this latest shutdown debacle, the Republicans always towed the party line. They've just recently started fighting with the Tea Party Republicans and it's about time they did that. They need to distance themselves from the element that thinks shutting down the Government and not raising the debt ceiling is the way to negotiate over a law that was already passed.