President-elect Donald Trump will nominate Republican U.S. Rep. Mick Mulvaney to be director of the White House Office of Management and Budget, a senior transition official said Friday.

An announcement naming Mulvaney is expected to be made Monday, according to the Wichita Eagle newspaper, which first reported that the South Carolina lawmaker had been chosen.

His nomination must be confirmed by the Republican-controlled Senate.

Mulvaney’s office did not immediately respond to a request for comment.

The OMB director plays a lead role in formulating budgets that reflect the administration’s legislative priorities and are a blueprint for detailed spending and tax bills the president wants Congress to consider.

Mulvaney, 49, is a fiscal conservative and was an outspoken critic of former House Speaker John Boehner, who resigned in 2015 amid opposition from fellow Republicans who were members of the House Freedom Caucus.

David Malpass, former chief economist with investment bank Bear Stearns and a senior Trump adviser, was also considered for the OMB job.