In the July 14 special election to choose the successor to former state Sen. Kirk Watson, Eckhardt received more than 60,000 votes and finished just a few hundred votes short of winning the vote outright without the need for a runoff.
The former Travis County judge was set to advance to a runoff election against fellow Democrat and state Rep. Eddie Rodriguez, but Rodriguez announced his concession July 27.
In a statement, Rodriguez's campaign said the District 51 representative, who represents a swath of Southeast Austin and Travis County, will focus his efforts on helping to win a Democratic majority in the Texas House of Representatives.
"I will be working hard for District 51 and the entire state, pushing a policy agenda that includes strong public schools, increased access to health care, gun violence prevention, meaningful criminal justice reform and policies that respect the dignity of every Texan."
Watson, who was initially elected to the state senate in 2006, resigned April 30 to take over as founding dean of the University of Houston Hobby School of Public Affairs. Eckhardt will serve out the remainder of the term through 2022 and will represent District 14 constituents at the 87th Legislative Session next year.
Rodriguez will be on the November ballot to retain his District 51 seat in the Texas House and will face Republican candidate Robert Reynolds. Rodriguez is the longest-tenured House member from Travis County; he has served since 2002 and is now seeking his ninth term at the Capitol.
