One possibility in 2020 is that we get a very weird primary: two old men most recently elected to office as independents competing for the Democratic nomination.

A choice between Michael Bloomberg and Bernie Sanders, however, might actually be the natural conclusion of the last 15 years in politics. Centrally, they each reflect the breakdown of the fundraising model that powered politics for a time — and the party structures that dominated politics for a century.

You saw a quick version of this dynamic play out on Thursday: Elizabeth Warren — the candidate who literally called for the rejection of super PAC funding — wouldn’t disavow the new super PAC that’s airing pro-Warren ads in Nevada.

“That’s how it has to be,” she said. “It can’t be the case that a bunch of people keep them and only one or two don’t.”

Later that night, the presidential campaigns released their January financial reports — a total wasteland of cash. Days before the Iowa caucus, Warren’s campaign had just $2.3 million left, with a $400,000 line of credit on the books. Pete Buttigieg had $6.6 million on hand, but at least some of that money can only be spent in a general election. Since then, Warren has announced fundraising deadlines, walked onto the debate stage with machetes, cut Bloomberg's head off, and taken in $17 million. Buttigieg is flying so much between rallies (and fundraisers) in Western states that he joked he isn’t always sure where he is anymore. These are the candidates who are first and third in the delegate count.

But we’re undergoing a major shift in the way politics work.

In the 1950s and ‘60s, television broke up the chokehold that big city machines held on national politics, pushing the parties toward more democratic caucuses and primaries. Congress instituted a public financing program that lasted, in various iterations, for the next 40 years. We’re seeing another shift in the mobile internet age as a result of specific finance decisions over the last two decades.

In 2000, George W. Bush declined to take public financing for the Republican primary, breaking with tradition; previously, candidates would receive matching funds from the government for their campaigns that capped fundraising. In 2008, Barack Obama declined to take general election public financing, blowing the doors off how much money candidates would raise thereafter. (John McCain, who took public financing, raised the maximum $84 million to Obama's $750 million in 2008.)

Fundraising for those campaigns (and still many campaigns now) ran on individual max-out checks: usually about $5,000 between a primary and a general, often “bundled” by someone on behalf of the campaign for efficiency and impact. But because of a series of Supreme Court rulings, donors by the early 2010s could create authorized super PACs — and the limits on joint-fundraising agreements between campaigns and the national parties went much higher. That meant, as you may have noticed with Donald Trump this time around or Hillary Clinton in 2016, that a presidential candidate can raise staggering sums of money through max-out checks to the party committees. On the strength of these developments, Obama, Clinton, Mitt Romney, the Republican National Committee, and a series of PACs raised and spent billions on presidential elections.

The situation by 2015: an outsize media and political obsession on whom big donors might favor in the Republican primary, and a Clinton operation that organized fundraising like they were retaking France. Meanwhile, you had a Republican Party machine presiding over a Trump nomination with essentially zero way to interfere, and a Democratic Party machine only able to favor Clinton by, like, limiting the number of debates.

In 2015, Sanders took the Obama-era innovations in online fundraising and advanced far beyond them, proving categorically that you could fund a national campaign without those $2,800 checks, reengaging the activist left in the process. Sanders raised $228 million, all from small contributions, premised on a highly ambitious, highly ideological platform. (He also had and has some super PAC support of his own, funded by a nurses union.) Sanders’ success — with all the validation conferred by votes, sway, and money — has already transformed the purview of Democrats from policy to style. The party's base for generations might really be far more in line with his ideas than anyone else’s; Sanders, more than any other politician in America, commands a multiracial base under the age of 30.