Before serving in the legislature, Schreiner worked as a middle school teacher, executive director of the Montana State Workforce Innovation Board, and as the director of work-based learning for the Montana Department of Labor and Industry.
In 2005, Schreiner earned a Bachelor of Science in cell biology and neuroscience from Montana State University.
[4] As Minority Leader, Schreiner succeeded in extending Medicaid expansion, which brought government-funded health care to nearly 100,000 low-income families; funding education; and passing a comprehensive infrastructure package.
[5] In the 2020 Montana gubernatorial election, Schreiner was a candidate for governor until withdrawing from the Democratic primary on February 3, 2020.
[6] On February 28, 2020, candidate Mike Cooney selected Schreiner to serve as his running mate.