On Monday, Rep. Mo Brooks (R-AL 5) announced his candidacy for the U.S. Senate in the special election to replace former Sen. Jeff Sessions (R-AL), now the attorney general.

Brooks will face at least four other GOP candidates in the August 15 primary, including incumbent Sen. Luther Strange R-AL),  former Alabama Supreme Court Chief Justice Roy Moore, State Rep. Ed Henry, and the Christian Coalition’s Randy Brinson. A runoff, if necessary, will be on September 26, and the general election will be held on December 12.

“I’m running for the United States Senate because the Senate has been a major barrier to solving America’s greatest challenges. Senate rules are antiquated, resulting in artificial barriers that thwart the majority will of the Senate and House of Representatives, as well as that of the president. More importantly, these arcane Senate rules thwart the will of the American citizens who elected the House, Senate, and president. It makes no sense that a Senate minority can grind the entire United States Senate to a halt, thereby inflicting so much damage on America,” Brooks told Alabama’s Yellowhammer News on Monday.

“I offer one thing no one else offers: honest, proven conservative leadership. While other candidates may claim the conservative mantle, I am the only candidate who has a long-term voting record that proves I not only talk the conservative talk, I also walk the conservative walk,” Brooks added.

Three Democrats, including former U.S. Attorney Doug Jones, are competing in the Democratic primary. The winner of the Republican primary is considered the odds-on favorite to win the general election in December.

Strange is considered a moderate establishment Republican and is supported by the Senate Leadership Fund, a well-financed Super PAC that “is closely aligned with Senate Majority Leader Mitch McConnell (R-KY).”

Both Brooks, who was first elected to Congress in the Tea Party wave of 2010, and Moore, who was suspended from his position as chief justice this year for what many conservatives describe as political reasons, are regarded as conservatives.

Heritage Action Scorecard rated Brooks the most conservative member of the Alabama delegation in the 112th Congress (2011-2012). With an 83 percent rating, he was slightly higher than the Alabama delegation’s second-most conservative member by the Heritage Action Scorecard at 77 percent: Sen. Jeff Sessions.

In the 113th Congress (2013-2014), Sessions and Brooks traded places, with Sessions rated the most-conservative member of the Alabama delegation, having an 85 percent rating and Brooks the second-most conservative member with a 75 percent rating.

In the 114th Congress (2015-2016), Brooks’ 94 percent rating placed him in second place in the Alabama delegation, barely behind Rep. Gary Palmer at 95 percent, but higher than Sen. Jeff Sessions, whose rating was 78 percent.

Despite Brooks’ conservative record in Congress, the Senate Leadership Fund launched an aggressive attack against him just minutes after he announced on Monday. Senate Leadership Fund spokesman Chris Pack said in a statement Monday morning:

While Luther Strange was cleaning up the corruption in Montgomery, Mo Brooks was living the life of a Washington insider, opposing Donald Trump and failing to get a single bill signed into law in four terms in the House. If Brooks can’t cut it in the House, how can he be trusted to deliver results in the U.S. Senate? It’s clear Mo Brooks is more interested in advancing his own career than he is with delivering for Alabama.

The Senate Leadership Fund is attempting to paint Strange as a reformer, but that narrative is facing heightened scrutiny in light of the manner in which Strange was appointed to the Senate in February.

Sessions was re-elected to a full six-year term in November. On February 9, former Gov. Robert Bentley appointed Strange, who was the Alabama attorney general at the time, to fill Sessions’ seat; he was sworn in on February 11. Bentley set the special election in which voters would select the senator to fill the remainder of Sessions’ term for November 2018.

Bentley, however, resigned in disgrace on April 10. Strange, as Alabama attorney general, chose not to prosecute Bentley for the conduct which ultimately led to his resignation.

Lt. Gov. Kay Ivey became governor upon Bentley’s resignation, and on April 18, she moved up the date of the special election to December of this year–eleven months earlier than the date Bentley had set.

The Alabama Political Reporter noted on April 18, the day Gov. Ivey announced the December general election date:

Former Gov. Robert Bentley balked at setting a special election, citing costs, and appointed former Alabama AG Luther Strange to the seat. Strange, who is the only announced candidate for the seat, would have held it until the regularly scheduled midterm elections in November 2018.

Roll Call was one of several media outlets to note that Strange’s track record is hard to reconcile with the Senate Leadership Fund’s characterization of him as a reformer dedicated to cleaning up corruption.

“Sen. Luther Strange’s new campaign ad leads with an image of politicians writhing in pain while getting sprayed down while standing in a car wash. According to the voiceover, this symbolizes Strange cleaning up corruption in Montgomery, Ala. during his time as state attorney general,” Roll Call reported on Monday, adding:

But in the two primary cases cited by Strange — the resignation of Gov. Robert Bentley and the prosecution of Alabama House Speaker Mike Hubbard — his role was more ambiguous.

In the case of Bentley, Strange is the subject of an ethics complaint with the Alabama State Bar over his handling of the former governor’s impeachment investigation. Bentley faced impeachment due to allegations of an affair and possible use of state resources to facilitate it.

“It appears that Sen. Luther Strange has egregiously violated his duty to his client, the State of Alabama,” the complaint by local lawyer and columnist Sam McLure reads, “by accepting Governor Robert Bentley’s appointment to U.S. Senate after stalling the Legislature’s impeachment investigation into Governor Robert Bentley and halting his own investigation in to Governor Robert Bentley.”

As Alabama Attorney General, Strange asked the Alabama House Judiciary Committee to suspend the impeachment investigation because he was conducting “related work.” The nature of that work was never revealed.

For his part, Brooks said that “Washington swamp critters” are backing Strange.