His performance came during a rally wrapping up a four-day march in support of Democratic state legislators who bolted for Washington two weeks ago to block Republican-backed voting restrictions.

Families with lawn chairs spread out across the sprawling Capitol greens in Austin. Clergy, politicians, constituents and musicians all spoke out about the proposals to impose voter ID requirements, limit ballot drop boxes and mail voting, and strip local officials of their election authority.

The special session that the exodus by Texas Democrats halted is set to expire next week, but Republican Governor Greg Abbott has pledged to schedule a new one as soon as the lawmakers return to the state.

"If you don't like who's in there, vote them out," Nelson sang, inviting the crowd to join him in singing lyrics he'd previously written about taking a stand at the ballot box.

The march began on Wednesday and ended on Saturday when participants walked up to the doors of the Texas Capitol building.

It was led, in part, by Beto O'Rourke, the former Democratic congressman and presidential candidate who has not ruled out a run for Texas governor in 2022.

Earlier this week, O'Rourke and marchers shut down the frontage road of Interstate 35 during the morning rush hour, funnelled between restaurants and cut a path from Republican-controlled statehouse districts to Democratic ones.

Marchers compared what the GOP says are measures meant to protect against fraud and restore confidence in American elections to Jim Crow-style restrictions. There has been no evidence of widespread fraud in the 2020 election.

"I ask you to think about every man and every woman who had the courage in their convictions and did what they needed to do in their own moment of truth in this country's history," O'Rourke told the crowd.

More than a dozen people in favour of the voting legislation proposed in Texas gathered at the Capitol building's front gate behind the rally, waving signs in support of the proposed changes.

Australian Associated Press