A Democratic senator is mounting a challenge to Chuck Schumer's leadership, a move cheered as a sign the party might finally listen to its voters.

• Chris Van Hollen is running for Senate Democratic leader against Schumer.
• He's described as unusually trusted by both the party's grassroots base and his fellow senators, having previously run Democratic campaign operations for both the Senate and House.
• Supporters are framing the race as a test of whether Democrats will change course after voters signaled they want a different approach, or stick with the status quo under Schumer.
• A call campaign is being organized urging voters to pressure their senators to back Van Hollen over Schumer.

Outlook: The outcome will hinge on whether enough Democratic senators side with grassroots pressure over party leadership continuity.