The DNC is caught in a bad spot. If Bernie wins the primary, they will most certainly lose the election, especially if the economy is strong.
BUT if Biden, who is seen by most as more likely to beat Trump wins the primary, a much worse scenario happens.
Embittered Bernie bros rebuffed for the 2nd election in a row by the media and DNC elites will most likely depress voter turnout by staying home, and that's no surprise considering Sanders is widely regarded as having more energetic supporters than Biden.
Will it affect the result of the presidential election? Who knows, but one thing IS for certain. Congressional seats are up for grabs in many Trump districts. If the vote for congressional seats is hampered by low voter turnout should Bernie get the boot, it will certainly hand that prize over to the GOP.