ANALYSIS: Why Michelle Obama and Bernie Sanders Are Key to Hillary Clinton's Chances

Michelle Obama and Clinton's primary opponent hit the trail today.

— -- Here come the reinforcements.

But those unlikely supporters are critical to the Clinton campaign’s efforts to solidify and energize the Democratic base this fall. The two former political foes of the Democratic presidential nominee hold distinct but distinctly important appeals for voters where Clinton has significant weaknesses.

Clinton is already getting the support of 9 in 10 black voters, according to the latest ABC News/Washington Post poll. But President Barack Obama got an even larger share.

The Clinton campaign hopes Michelle Obama drives up interest among those who were more enthusiastic to cast ballots for her husband than they are to vote for Clinton.

“Let’s face it, elections aren’t about who votes. It’s about who doesn’t vote,” Michelle Obama said at a campaign event today in Philadelphia.

Then there’s Sanders, who did real damage to Clinton, particularly among independents, over the long primary battle few thought he would endure. New Hampshire was his breakthrough state against Clinton, and that’s where he campaigned with her this afternoon.

Michelle Obama and Sanders were political opponents of Clinton’s before this campaign.

ABC News’ Adam Kelsey and Ryan Struyk contributed to this report.