Testimony will be heard from those in charge of managing rivers as well as emergency managers and first responders about the flash flooding that killed at least 135 people.

Democrats want to address flood relief and new flood warning systems before taking votes on new congressional maps sought by President Donald Trump.

Voting on new congressional maps before any response to the Hill Country floods could create a political liability for Republicans, who control all levels of Texas government. Texas is still reeling from the disaster, which is one of the worst in the state’s modern history, and few Texans have voiced concerns about the state’s political maps.

Texas Republicans want to redraw the state's congressional districts to gain an advantage in next year's election. U.S. Rep. Ritchie Torres, D-N.Y., says Democrats must counter or become complicit.

The governor eventually agreed to include redistricting on his special session agenda after discussing the matter with the president on a phone call.

President Trump is pushing Texas to redraw its congressional map to favor Republicans - a plan Beto O’Rouke is warning could backfire on the GOP nationally. NBC News’ Ryan Chandler reports from Dallas on Governor Abbott’s special legislative session.