After gaining national prominence as one of President Donald Trump’s biggest defenders during last year’s Democratic-led impeachment hearings, U.S. Rep. Doug Collins announced his bid on Wednesday to become Georgia’s newest senator.

Collins will challenge the newly appointed Kelly Loeffler in a special election later this year. Loeffler, also a Republican, was named by Georgia Gov. Brian Kemp to fill out the unexpired term of Johnny Isakson, who retired last year due to health concerns.

Collins is the ranking Republican on the House Judiciary Committee, chaired by U.S. Rep. Jerry Nadler.

U.S. Rep. Adam Schiff, a California Democrat and chairman of the House Intelligence Committee, led the charge to impeach the president, but Collins gained national prominence as one of Trump’s leading defenders on Capitol Hill.

»MORE: Georgia's Collins takes lead role as impeachment probe enters new stage

A native of Gainesville, Georgia, Collins was elected to represent the 9th District in 2012. Collins’ father was a Georgia state trooper, and his mother provided care to local senior citizens.

After graduating from North Hall High School, Collins earned a degree in political science and criminal justice from the University of North Georgia, and then interned in the U.S. House of Representatives.

U.S. Rep. Doug Collins is preparing to challenge Sen. Kelly Loeffler. It presents a tense situation that will force state Republicans to draw battle lines within their own party at a precarious political moment.

Collins then earned a master’s degree in divinity from New Orleans Baptist Theological Seminary. In 2006, he was elected to the state House and soon became the governor’s floor leader.

As a U.S. Air Force Reserve chaplain, Collins was deployed to Iraq in 2008-09 and holds the rank of lieutenant colonel.

As one of the fiercest critics of the House's impeachment hearings, Collins gained Trump's attention as the battle over who would replace Isakson developed.

Gov. Brian Kemp is set to appoint financial executive Kelly Loeffler to an open U.S. Senate seat. President Donald Trump was forcefully advocating for U.S. Rep. Doug Collins instead. So why did Kemp decide on Loeffler?

Kemp’s office was flooded with candidates after Isakson announced his retirement.

»READ: Johnny Isakson delivers Senate farewell speech

One of those was Collins, who actively sought the seat. During a late 2019 trip to Atlanta, Trump personally asked Kemp to appoint Collins to fill out Isakson's unexpired term.

Kemp, however, chose Loeffler, a wealthy business executive.

Loeffler's appointment drew the ire of some conservatives and Republicans, including Fox News commentator Sean Hannity.

Kelly Loeffler is chief executive of Bakkt, a subsidiary of Intercontinental Exchange. In 2011, she bought a stake in the WNBA's Atlanta Dream. Loeffler supported Mitt Romney for president in 2012. She considered running for U.S. senate in 2014 in Georgia. Loeffler is also a supporter of President Donald Trump.

Collins is certain to continue leading Trump’s defense in Congress.

“It’s easy to argue when you have truth on your side,” Collins told The Atlanta Journal-Constitution recently. “Whether that shows me as a defender of the president, which it is, or whether that shows me and our Republican conference is tired of the attacks from the Democrats on a duly-elected president for what is no reason for impeachment, then so be it.”