Former Kansas Secretary of State and general counsel for We Build the Wall, Inc. Kris Kobach is announcing his U.S. Senate candidacy on Monday.

Kobach is declaring his run for Senate in Kansas following Sen. Pat Roberts’ (R-KS) announcement earlier this year that he would not be seeking re-election after holding the seat since 1997.

A staunch ally of President Trump and his “America First” agenda, Kobach has served as an advisor to the president on immigration issues and devised a plan for the administration that would instantly end the catch and release of border crossers and illegal aliens into the U.S. by Department of Homeland Security (DHS) officials.

“Not since Jeff Sessions has the Senate had a leader on immigration who defends the American worker and knows the issue inside and out,” an insider told Breitbart News. “Kobach would fill that void.”

Kobach previously worked at the Justice Department in the early 2000s for then-Attorney General John Ashcroft and created the National Security Entry/Exit Registration System (NSEERS) — the first entry/exit system in U.S. history — after the September 11, 2001 terrorist attacks. The NSEERS program provided U.S. officials with a streamlined process for registering, fingerprinting, and tracking legal immigrants deemed to be “high-risk” due to their ties to state-sponsors of terrorism.

Kobach is also widely known as one of the architects of Arizona’s mandatory E-Verify law — the policy that bars employers from hiring illegal aliens over American citizens — which was ruled constitutional by the U.S. Supreme Court and which inspired states like Mississippi and Alabama to also adopt similar E-Verify laws that protect American workers from unfair foreign competition.

The GOP primary for the open Senate seat could be a crowded field of Republican contenders. Kobach joins lesser-known candidates State Treasurer Jake LaTurner and former Kansas City Chiefs player Dave Lindstrom in the race. Also likely to announce a run is Kansas Chamber of Commerce President Alan Cobb.

On the Democrat side, former U.S. Attorney Barry Grissom has announced his run and others like state senator Barbara Bollier and Rep. Nancy Boyda (D-KS) are expected to get in the race as well.

John Binder is a reporter for Breitbart News. Follow him on Twitter at @JxhnBinder.