MSNBC asked Benjy Sarlin, its reporter on the Republican race, and Alex Seitz-Wald, its reporter on the Democratic race, to flip jobs for a week and write up what they learned. Their conversation is worth reading in full, but something Sarlin wrote caught my eye:

I was caught off guard by how specific and personal Democratic voters’ issues tended to be. One woman told me she had lost a job because she had to take care of a sick relative and wanted paid family leave. Another woman told me her insurance stopped covering a certain medication that had grown too expensive and she liked how Clinton and Sanders talked about lowering drug prices. One man told me his wages were stagnant at his hotel job and he was looking for policies to increase them. "We’re talking about bread-and-butter issues," Phyllis Thede, an Iowa state representative backing Clinton, told me when I asked about her constituents’ top concerns. By contrast, Republican voters tend to be excited by more abstract issues: One of the most common answers I get from Cruz voters when I ask about their leading concern is "the Constitution." There are fewer "I have a specific problem in my own life, and I’d like the government to do x about it" responses.

Sarlin's observations mirror interesting research from Matthew Grossmann and David Hopkins about how Republicans and Democrats differ. Their main finding is that Democrats are motivated by specific policy deliverables while Republicans are motivated by broader philosophical principles. But behind this finding is some interesting evidence.

Democrats like compromise; Republicans don't

Democrats prefer politicians who compromise, and Republicans prefer politicians who stick to their principles. This is true even when a Republican holds the presidency:

"Though they voiced strong disapproval of Bush, Democrats still expressed a preference for compromise in government — a tendency that has carried over to the Obama era," write Grossmann and Hopkins. "Republicans have been consistent in their elevation of principle over moderation, regardless of which party is in power."

Democrats rely on more interest groups than Republicans

The ecosystem of interest groups making endorsements on the Democratic side is both larger and more interconnected than on the Republican side — which means there are more organized groups asking Democrats for policy than asking Republicans for policy.

You can see that in this graphic, which connects interest groups that endorsed more than one of the same candidate or bill in the 2001-'02 Congress and the 2002 midterm election. So if the AFL-CIO and the Sierra Club both endorsed Sen. Pat Leahy for reelection and also both endorsed No Child Left Behind, they get a line. The more shared endorsements between two groups, the thicker the line connecting them; the more total connections any individual group has to other groups, the larger the circle they get.

But Democratic interest groups aren't just more numerous; they're also more persistent. "The Democratic Party contains strong links between its electoral and legislative coalitions. ... The diverse groups that come together to support the same candidates also ally when it comes to passing bills in Congress," write Grossmann and Hopkins. "The Republican Party lacks similar ties between its electoral and legislative coalitions, mostly because few of its groups regularly join coalitions to support or oppose legislation."

Policymaking has a liberal bias — even when Republicans do it

Democratic presidents talk more about policy, propose more specific policy ideas, and pass more significant pieces of legislation. The numbers are stark. Since 1945, Democratic presidents have put forward 39 percent more policy proposals than Republican presidents, and 62 percent more domestic policy proposals.

"There is a good reason for this asymmetry," write Grossmann and Hopkins. "Democrats and liberals are more likely to focus on policymaking because any change that occurs is much more likely to be liberal than conservative. New policies usually expand the scope of government responsibility, funding, or regulation. There are occasional conservative policy successes as well, but they are less frequent and are usually accompanied by expansion of government responsibility in other areas."

VIDEO: Lawmaking has a liberal bias

Why there's no Democratic tea party

I've often heard liberals wonder why there's no Democratic version of the Tea Party. I've often heard conservatives complain that their party doesn't spend enough time coming up with serious policy solutions for issues like health care. And, to be sure, there are some liberals trying to popularize Tea Party–like tactics and some conservatives trying to come up with sweeping new health reforms.

But it's hard for these initiatives to succeed. There's a tendency to imagine the parties as mirror images of each other, and thus to believe they can easily follow the other's strategies. But they can't. The parties are good at different things because they really are different.

That difference, however, can lead to deep misunderstandings. Democrats tend to project their preference for policymaking onto the Republican Party — and then respond with anger and confusion when Republicans don't seem interested in making a deal. Republicans tend to assume the Democratic Party is more ideological than it is, and so see various policy initiatives as part of an ideological effort to remake America along more socialistic lines.