The political season in the District kicks off this week, as candidates start picking up qualifying petitions in preparation for party primaries on April 1. Whether they are vying to become the next mayor or to join the D.C. Council, where six seats are in play, an indisputable liberalism connects the known contenders.

The question is which brand of liberalism will come out on top. As of Aug. 31, nearly 76 percent of the city’s 469,913 voters were registered Democrats. Despite its dominance, or perhaps because of it, the city’s Democratic Party appears to be fracturing. The battle is between old-line liberals and progressives — an identification without a cogent, consistent distinction.

“If you ask nine people what it means, you probably will get nine different things,” admitted Bryan Weaver, a progressive candidate for the Ward 1 council seat currently held by Jim Graham (D); Graham hasn’t announced whether he’ll run for reelection.

“In a one-party town, with one machine, progressives work beyond that machine to break down the status quo,” continued Weaver.

Some people I spoke with while writing this column have called the city’s posse of progressives inconsequential. Perhaps they missed progressive Bill de Blasio’s win this week in the New York mayoral race. Pollster Jef Pollock told The Post that de Blasio’s victory showed that “old-school, coalition politics, where we just assume that people are going to vote for the candidate who looks and sounds like them . . . has been broken.”

Last year in the District, progressives helped David Grosso (I) win an at-large council post, while Elissa Silverman placed a surprisingly strong second in last April’s special at-large council election.

Those results have emboldened progressives, who have vowed to reshape the city’s politics and culture. “It’s about shattering some of those connections that form a politics of a bygone era,” said Weaver.

Does that spell trouble for traditional liberals such as Jack Evans (D-Ward 2) and Muriel Bowser (D-Ward 4), considered early front-runners for the Democratic mayoral nomination?

“I fashion myself as a responsible social-progressive candidate,” said Evans, citing his record of strong support for gay rights, rent control, tax relief for low-income residents and senior citizens and affordable housing.

But progressives don’t claim him. They think he’s too chummy with the business community — although Evans supported the anti-Wal-Mart Large Retailer Accountability Act, which was pushed by progressives. (See what I mean about inconsistency?) The mayor eventually vetoed the bill.

The primary election will undoubtedly expose these growing divisions, which already have received an airing during the debate on raising the minimum wage. Progressives have demanded an end to “pay-to-play” policies and practices that have abetted government corruption, called for greater transparency and pushed for stronger campaign finance reform, arguing that legislation advanced by Council member Kenyan McDuffie (D-Ward 5) and recently approved by the majority of the legislature doesn’t go far enough.

Progressives also have advocated providing more shelter space for the homeless and more affordable housing for others, as well as changes in the city’s tax structure. Some have pressed for changes in the District’s drugs law — many want to turn marijuana into a legalized, though regulated, substance.

Can the District afford their agenda? Tax deductions cost money. Legalizing marijuana would mean an expansion in the bureaucracy and more spending. The city may not be in danger of returning to its nearly bankrupt state of the mid-1990s, but the federal shutdown revealed the precarious nature of the District’s economy.

“Old-line liberals . . . just want to give more money to problems,” said Tommy Wells (D-Ward 6), who is running for mayor. “[But] it’s not how much money you give to people [on welfare] or schools. Progressives are focused on the results or outcomes from those investments.”

There’s some overlap between these types of Democrats, of course, but here’s a key distinction: While both types focus on the standard fare of social ills, they differ in how they approach the issues. Unlike old-line liberals, progressives aren’t satisfied with massaging problems or tweaking solutions; they tend to seek large-scale, structural change that upsets the status quo. For example, instead of simply increasing the standard deduction for low-income residents, they may push to change the entire tax code. For them, the ultimate policy goal is dramatically reducing income inequality — not just winning one or two additional benefits for those who need them.

Wells has been perceived as the pied piper of progressives since he helped them surface during a fight over the H Street NE streetcar. He has pushed good-governance issues and advocated for decriminalization of marijuana to deal with what has been called the unjust arrest of those possessing small amounts of the drug. But he voted against the anti-Wal-Mart bill, and said he became a target of the more radical faction of his group as a result. Those are the folks living in the far reaches of the party’s left wing.

The District doesn’t hold an open primary. Consequently, the greatest amount of action will be among Democrats. It’s probably unsurprising they are gnawing at each other. We will have to wait to see if the infighting proves beneficial, resulting in the election of innovative and visionary leaders capable of taking the city to the next stage.