Rep. Ron DeSantis, a conservative Republican running for governor of Florida, has resigned from the House to focus on his campaign, he told House Speaker Paul Ryan in a letter delivered Monday.

DeSantis, 39, has represented Florida’s 6th Congressional District since 2013. He faces Tallahassee Mayor Andrew Gillum, a Democrat, in a closely watched race this November.

“As the Republican nominee for governor of Florida, it is clear to me that I will likely miss the vast majority of our remaining session days for this Congress,” DeSantis wrote. “Under these circumstances, it would be inappropriate for me to accept a salary. In order to honor my principles and protect the taxpayer, I officially resign from the House of Representatives effective immediately.”

A spokesman for Ryan confirmed receipt of DeSantis’ letter.

DeSantis’ announcement comes as Gillum, who has seen an influx of support from progressives and national Democratic groups, has opened up an early fundraising lead for the general election. According to Florida campaign finance reports filed Friday, Gillum has raised $4 million since winning the Democratic nomination Aug. 28. DeSantis raised $516,000 during the same period.

DeSantis also has been hobbled by questions about his racial sensitivity and past association with a far-right activist who has expressed controversial views about race. Last week, DeSantis scrambled to contain outrage from Florida voters after he urged the state not to “monkey this up” by electing Gillum, whom he accused of being a socialist.

On Sunday, The Washington Post reported that DeSantis had spoken four times since 2013 at a conference organized by David Horowitz, a conservative firebrand who has stated that “African-Americans owe their freedom to white people and that the country’s ‘only serious race war’ is against whites.”

On Monday, several Florida-based progressive and racial justice groups called on DeSantis to withdraw from the governor’s race.

“As his true colors keep getting clearer, the real question is, how can anyone continue to stand with DeSantis,” said Dwight Bullard, political director of the left-leaning New Florida Majority, which aims to diversify Florida’s political ranks.

Gillum’s running mate, Chris King, issued a statement saying DeSantis has “serious questions to answer to Floridians about why he repeatedly chose to attend these events.”

Other than his statement announcing his resignation from the House, DeSantis stayed out of public view during the day Monday. He was to appear at his “campaign kickoff” Monday night in Miami with his running mate, Florida state Rep. Jeanette Nuñez. Nuñez is Cuban American, a demographic that makes up a pivotal Florida voting bloc.

DeSantis has missed 43 of 80 House votes cast since July – including all 14 votes last week – according to a database maintained by GovTrack. In his letter to Ryan, DeSantis asked that his resignation be made retroactive to Sept. 1 for payroll purposes.

“This is not a decision I make lightly,” he wrote. “It has been an honor to serve the people of Florida’s Sixth Congressional District, and I look forward to serving them and the rest of Florida as our state’s next governor.”

A member of the hard-right House Freedom Caucus, DeSantis has emerged as one of President Trump’s most aggressive defenders on Capitol Hill and has been a critic of the Justice Department and special counsel investigations into Trump.

DeSantis is one of six sitting House members seeking governor’s seats across the country. Gubernatorial candidates remaining in the House are fellow Republicans Kristi Noem of South Dakota and Stevan Pearce of New Mexico, as well as Democrats Tim Walz of Minnesota, Jared Polis of Colorado and Michelle Lujan Grisham of New Mexico.