Las Vegas - Hillary Clinton's use of a private email server has shadowed her campaign through a difficult summer. But when it was invoked Tuesday at the first Democratic presidential debate, she got help from an unlikely source: her fiercest rival.

“Let me say something that may not be great politics,” said Vermont U.S. Sen. Bernie Sanders of Clinton, whose use of the server while secretary of state is under attack by Republicans. “I think the secretary is right. The American people are sick and tired of hearing about your damn emails.”

It was the standout moment in a debate that largely revolved around Clinton, the front-runner for her party’s nomination, as she carefully worked to avoid any missteps that could give her challengers an opening.

No, it was not the rollicking affair that helped the first two Republican debates shatter ratings records for their cable news hosts. (There was no Democratic version of Donald Trump, after all.) But it offered sharp contrasts — and a few gripping moments — that could define the Democratic campaign ahead.