There are those who claim there is little, if any, daylight between the establishment parties and there are those who describe them as being akin to malcontents.
'there is NO difference between the parties' are obvious trolls that MIRT boots very quickly, and are about as rare as unicorns, even nuclear ones.
What almost everyone else says, that is frequently misquoted as 'no daylight between' by people wanting to caricature those folks as malcontent (and really, about the only more establishment-speak you could get beyond calling them 'malcontents' is to call them 'dissidents'. I can only assume your choice of the anarchy symbol as your avatar is highly ironic, given your investment in the established party.) is 'the parties are obviously far apart on social issues, but far too often much more similar on foreign military adventurism (drones, black ops, ongoing large numbers of American troops in countries in turmoil despite 'the end' of 'combat'), "homeland security" (domestic surveillance that makes the 4th amendment look like a quaint joke, militarized police, and joint operations between the two to disrupt civilian protests), and overarching economic policies that keep the richest getting even richer and the rest of us owning an ever shrinking slice of the pie, and ever more of us unemployed and not even counted in the statistics.
So sure, there is plenty of daylight on a narrow range of issues. And there are a smaller subset of Congressfolks on the left who are good on the other issues as well, but not enough to break the party apart from the Repubs on the issues of keeping the powerful powerful and the poor in line.
You'd think that with all this daylight things would look sunnier.
keep steadfastly to policies that favour the rich (ie, themselves). In large part because you have to be rich or have a lot of rich patrons to run for office, which puts pressure on to make those patrons happy.
Republicans tend to do it with blunter, more easily understood policies, like switching from income taxes to sales taxes. Democrats at least usually try to obfuscate what they're doing in more complex policies that give some benefits to the poor, but ensure that even more money will flow to the rich. With TTP and TTIP, they tried simply to hide it from view entirely, until it's fait accompli. But thankfully, as I said, there are some smaller number of good Dems who break with the party - my Senator, Sherrod Brown, Elizabeth Warren, Bernie Sanders (ok, not a Dem, but he caucuses with) and so on. Probably not enough to swing things outright, but maybe, just maybe, enough to get enough citizen outrage raised, ok, strike that, they just announced a deal was reach on fast-tracking it, and think they've got enough votes to do so. I hope they're wrong.