Dana Haswell Corbin had no idea she was bucking conventional political wisdom when she wore her pale blue “Bernie for President” T-shirt months before a primary vote in any state, let alone her native Pennsylvania.

Conventional wisdom dictates she is supposed to like Hillary Clinton's “unique and historic candidacy” as a woman on the cusp of walking away with the Democrats' nomination. But Corbin says she likes Bernie Sanders, Vermont's “democratic socialist” U.S. senator, because of what she describes as his frank talk and his authentic voice on progressive issues.

Corbin's sentiment is by no means a trend away from Clinton that could crest into a wave of revolt against her, in spite of Sanders making gains against Clinton in two recent opinion polls. Yet Corbin is symbolic of the tug-of-war among Democrats.

“The war for the progressive heart rages in the open, now that this political faction has won outright control of the Democratic Party,” explains political scientist Curt Nichols, a Kinder Fellow at the University of Missouri.

“The soul-searching gets intense when the choice is between remaining pure to one's protest-oriented roots and compromising to get and maintain a hand on the lever of presidential power,” he said.

Nichols said the same angst-filled struggle took place among supporters of Germany's Green Party in the 1980s: “There, members of the fundamentalist ‘fundis' group argued the party must stay true, and damn the electoral consequence.”

The Greens' “realos” wing advocated being realistic and compromising to gain a share of power. The realos won the argument, formed a red-green coalition with the Social Democratic Party, and helped lead the government for many years.

“While the American political tradition may lack the language to describe this conflict, the fact is that a very similar battle is occurring within the ranks of the progressive movement today,” said Nichols.

Indeed, the progressives' melee rages on while being shielded from easy comprehension by an umbrella of less precise, ultimately misleading terminology.

The “fundis” of American progressive politics — exemplified by the likes of Sen. Elizabeth Warren, D-Mass. — have taken to calling themselves populists. They disparage the “realos” progressives — like President Obama and Hillary Clinton — for being too cozy with big banks and corporate interests.

Never mind that conservatives can scarcely tell the difference between the two wings of the progressive political faction.

It strains history (and one's brain) to the breaking point to conceive of a former Harvard Law School professor — Warren's previous occupation — as being the heir apparent to the anti-elitist, agrarian-oriented “People's Party” of William Jennings Bryan's day.

A rose is still a rose if called by another name. So, too, with a “fundis” progressive who chooses to call herself a populist.

In short, while the progressive movement is growing within the Democratic Party and, at least for now, is winning the struggle to control it, it also is experiencing an identity crisis.

The power to steer the future course of the party hangs in the balance; the choice is between the purism and electoral kryptonite offered by the fundamentalist sect and the more centrist-appearing (but equally subversive) compromising tactics endorsed by the realists.

The fascinating thing about this struggle is that, on the surface, Washington pundits and establishment Democrats treat this as the struggle of which we dare not speak — a phenomenon that, in theory, should anger activist Democrats. This is, after all, a major American political party that currently holds the White House.

Is there a reluctance to speak because the pundits do not understand what is happening? Or lack the intellectual curiosity to explore it? Or, worse yet, want to hide the struggle under the rug and hope it will go away?

When Republicans have faced their demons — for example, the faux tea party people, not the authentic original movement — it was a very public, very examined, often very embarrassing dissection of the direction of the Grand Old Party. For Republicans, 2012 was ugly; by 2014 they had straightened themselves out.

Reporting on party soul-searching like that is often uncomfortable, yet necessary to understand the realignment that regularly occurs in American politics. Progressive activists should demand that their laundry be aired out.

Salena Zito is a Pittsburgh Tribune-Review editorial page columnist. E-mail her at szito@tribweb.com