Political scientists in their studies of American politics often focus on the median voter–the voter who just perfectly positioned so that one-half of the electorate is more liberal and the other half is more conservative. In theory, both major parties jostle to move close to this mythological voter to win the election.

Despite the seeming incentives for the parties to act like Tweedledee and Tweedledum, they also face pressures to distinguish themselves. Parties that become too centrist get pressed by third parties. In New York, the Conservative Party can threaten to refuse to cross-endorse Republican candidates who are too moderate. Democrats can similarly face challenges from the Green Party.

From a branding perspective, a little distinctiveness also helps. No one would go to Five Guys if their advertisements said “We’re just like McDonald’s!” Distinct issue positions are also a much cheaper way for parties to attract votes than political patronage–now severely limited by civil service laws.

But the real pressure to move away from the center comes from party primaries. In Democratic bastions like Baltimore City, and Montgomery and Prince George’s County, the Democratic primary is the election for all intents and purposes. Of course, the same applies for Republican primaries in Republican jurisdictions.

Pols running in these places naturally orient their campaigns to the primary rather than the general electorate. Voters have become increasingly well sorted into the parties based on ideology so composition of each party’s adherents is increasingly starkly different. Primaries accent this effect as they tend to attract the more diehard voters.

The result is parties that radically rather than mildly disagree, especially since so many politicians run in safe seats. Republicans take extreme positions utterly out of the mainstream on any number of issues from immigration to LGBT equality to the minimum wage because their primary electorates demand it. This is why we got to watch the long spectacle of Mitt Romney turning himself inside out as an ideological pretzel during the 2012 primary season.

Democrats have not moved as nearly as far to the left as Republicans have moved to the right (see Tom Mann and Norm Ornstein’s argument and the statistics on voteview.com). Democrats, however, are hardly immune to same effect. Conservative Democrats are basically gone and moderate Democrats are fewer in number.

Maryland, surprisingly, despite its liberalism retains somewhat greater diversity among elected Democratic legislators. This is most certainly not from a failure to elect liberals from liberal districts but from Democratic Party savvy at running  and then supporting more moderate candidates in places where needed–historically a real party strength. Combined with Republican electoral ineptitude, this strategy has helped balloon Democratic numbers in both houses of the General Assembly.

Nonetheless, Maryland is increasingly going to see efforts by candidates in liberal areas to play leapfrog and out-progressive other candidates. After all, that’s where the voters are in Democratic primaries. Witness Del. Heather Mizeur’s efforts to distinguish herself as the left-wing Democrat in the gubernatorial race. The result can be a war of outbidding–try to prove one is more truly left-wing, progressive, liberal (pick your poison) than the other other candidates.

Of course, there are smarter and dumber versions of this strategy. Heather takes the smarter one by emphasizing progressive issues that attract a broad spectrum of Democrats even as she smartly proves her relative liberalism. She had a nice coup when Lt. Gov. Brown said “me-too” in shifting towards her position on medical marijuana (h/t Maryland Juice).

While the candidates will stress these differences, they are small in the broad scheme of things. Recall the Clinton-Obama magical mystery tour of debates, which one can pretend came down to profound issue differences but really divided people based on who you thought ought to be president. (Perhaps we’ll get both in the end?)

Outbidding can be deleterious in a number of ways. First, it encourages candidates to adhere to the shibboleths of each party rather than deal with practical issues. It makes politics feel more like praying at an especially fervent denomination rather than a way to solve problems. I can already envision some candidates accusing others of heresy because they happen to disagree in a minor way how to move forward on this or that issue.

Unlike when shopping for water, this should not be a purity test. Yep, we want someone who agrees with us on the issues. But we also want someone who we think is up to scratch in running the State and has the vision to move us forward in a positive direction.

In sum, Democrats can be liberal and not stupid (I think Barney Frank said it or something similar originally) by not following the Republicans into our own version of teahadism without giving up our core values.