When the primary season started, there were 18 Republican candidates and 3 Democratic hopefuls.

In a twist of irony of roller-coaster-sized proportions, the Republicans have their presumptive nominee while the Democrats are still engaging in an intense ballot battle.

The fight for the nomination continues with Senator Bernie Sanders’ upset win in Indiana.

Bernie Sanders triumphed over Hillary Clinton in Indiana’s open primary Tuesday, boosting the grassroots candidate’s argument that the party’s superdelegates should flip their support to him in July’s Democratic convention.

Sanders spoke to thousands of supporters in Louisville, Ky., before Indiana’s results were in. He called for an end to closed primaries and criticized Clinton for her ties to Wall Street and paid speeches to Goldman Sachs — a sign the heated rhetoric on the Democratic side shows no signs of cooling down.

This win is critical, because Hillary cannot quite create the narrative that Donald Trump now can about being the likely nominee. That is, unless she relies on those superdelegates.

But doing so is not enhancing her popularity among Sanders supporters.

Political analyst Nate Silvers sympathizes about how unfair the superdelegate system is, and offers those who #FeelTheBern a little hope:

Superdelegates were created in part to give Democratic party elites the opportunity to put their finger on the scale and prevent nominations like those of George McGovern in 1972 or Jimmy Carter in 1976, which displeased party insiders.

Here’s the consolation, however. Unlike elected delegates, superdelegates are unbound to any candidate even on the first ballot. They can switch whenever they like, and some of them probably will switch to Sanders if he extends his winning streak into more diverse states and eventually appears to have more of a mandate than Clinton among Democratic voters.

Sanders may capture a couple of more primary wins in Oregon (where he enjoys a large margin in the polls) and West Virginia (where Clinton’s statements about coal mines have hurt her chances).

Significant momentum for the Vermont Senator could be gained if he takes California in the June 7th primary. Unfortunately, Bernie Fever does not seem to have reached the Golden State…yet. He has just narrowed the margin to 2 points:

Hillary Clinton’s lead over rival Bernie Sanders in California has shrunk to two points, bringing to a screeching halt any momentum she hoped to gain from her 16-point win in New York.

The Fox poll out Friday night showed Sanders surging in the Golden State, where two earlier April polls had him 6 and 12 points behind.

Finally, Sanders’ Indiana win means Clinton can not entirely focus her attacks on Trump, because she has to watch her left flank. The struggle in the Democratic Party could provide some useful weapons for Trump during November’s epic battle.

“Crooked Hillary — is there anybody more crooked than this woman? No, is there anybody?” Mr. Trump said at a Thursday rally in Harrisburg, Pennsylvania. “You know Bernie Sanders, who in all fairness, and I have to tell you in all fairness, he said she has bad judgment, all right? She does.”

“He’s been tough on her,” Mr. Trump said. “In fact, I’d like him to keep going, because the longer he goes, the more I’m going to like it.”

“What he’s saying about her … he said she suffers from bad judgment,” Mr. Trump said. “Now, I don’t know. I think she’s qualified, I guess, but that doesn’t mean she’s good.”

“He said she’s not qualified to be president,” Mr. Trump said. “Now what he meant is because her judgment is so bad, so Bernie Sanders — not me — said she’s not qualified. So now I’m going to say she’s not qualified, OK?”

Honestly, who would have thought the more exciting ride would have been on the left this primary season?

(Featured Image: CBS News Video)