My state representative, Daniel Kagan (D-HD 3), offers up an assessment at Colorado Pols of what features make the Colorado General Assembly better than the United States Congress, which is spot on in capturing the differences in political culture and process between the two bodies. Colorado legislative politics are civil and not quite as partisan as those as federal legislative politics despite having a rather similar partisan balance to the federal government. The post captures his characteristically constructive tone in legislating.
A structural approach to political theory struggles to explain why this is the case. The election rules for the Colorado General Assembly aren't materially different than those of the federal government, although Colorado legislators are term limited while federal ones are not. Colorado has a different set of procedural rules, but they could be rewritten or ignored with impunity if the political culture were different. Indeed, there are plenty of examples of procedural rules that are ignored in spirit, if not form, in the Colorado General Assembly (like the provision allowing the legislature to speed up the effective date of a bill with a "safety clause"), and the "single subject" rule he cites, while applied with rigor to initiatives, is applied largely voluntarily and with a light judicial touch to enactments of the General Assembly. The bicameral process with an executive branch veto is also similar, although Colorado lacks the filibuster power found in the U.S. Senate and doesn't allow legislators to participate in judicial appointments. It might have something to do with the fact that the Colorado General Assembly has a more manageable 100 members for both chambers combined, while the U.S. Congress has 535 voting members. One could argue that the stakes are higher at the federal level, but on some of the highest stakes decisions faced in Washington but not Denver, like deciding whether or not to go to war, partisanship is at its weakest, and states have plenty of high stakes decisions, like whether to adopt the death penalty, to resolve.
Another plausible possibility is that there is less of a culture divide between politicians of the two parties in Colorado than there is in the United States as a whole. Politicians from Denver and Montrose have more in common with each other culturally than politicians from New York City and Biloxi do. Colorado's GOP was influenced by the Tea Party movement, but not entirely replaced by it.
It could also be the case that the reality of state government, in which there are requirements like balanced budgets, TABOR, federal spending program limitations, and a much more detailed state constitution, refines the sense of politics as the art of the possible at the state level and that the best is the enemy of the good.
Whatever the reason, the fact that two superficially similar systems can feel so different from the inside illuminates what really matters in a political system.