Rep. Bob Turner (R-N.Y.) announced Tuesday he will challenge Sen. Kirsten GillibrandKirsten Elizabeth GillibrandTrump thinks he could easily beat Sanders in 2020 match-up: report Listen: EMILY’s List upbeat about Dem House in '19 Desperate Democrats shouldn't settle for Oprah MORE (D-N.Y.) this fall rather than run for reelection in the House.

His district is expected to be dismantled once the state finalizes its congressional map.

"Brooklyn and Queens voters, of all political parties, graciously responded by sending me to Congress," Turner said in a statement. "It now appears that their district has been eliminated."

Turner's district had long been on the chopping block. New York lawmakers needed to eliminate two districts to accommodate population change, and when former Rep. Anthony Weiner (D-N.Y.) stepped down in 2011, both parties looked to that district.

Turner won a special election to replace Weiner later in the year with the awareness that the district might not exist much longer. Republicans touted his win in the Democratic-leaning district, and the area's large population of Orthodox Jewish voters were credited with helping his victory.  His win was also seen as a referendum on President Obama’s Middle East policies.

New York state lawmakers have gridlocked for months on the state's new congressional maps, and a federal court panel intervened to propose their own map, which sliced up Turner's district and left him no district where he could run without challenging an incumbent member. It is not clear whether the court-drawn map or a last-minute proposal by state lawmakers will eventually take effect.

"I am prepared to run in whatever district I reside in once the final lines are adopted," Turner said last week when the court-drawn map was proposed.

But Turner said Tuesday that he has told the other GOP candidates that he plans to enter the race against Gillibrand. There are three other Republicans running: hedge fund manager Joseph Carvin, attorney Wendy Long and Nassau County Comptroller George Maragos.

Turner is best known of the three. He said he will seek both the Republican nomination and the endorsement of the Conservative Party, which plays an influential role in the nominating process.

"I will travel to the Republican State Convention in Rochester later this week and humbly ask for the Republican nomination for the United States Senate," Turner said in his statement. "I will respectfully ask for the Conservative nomination a few days later at that party's convention.”

An aide to Turner said the lawmaker is staying in the race even if New York's final maps don't dismantle his House district.

"There is serious work to be done to get this economy back on track, and I will not walk away from that work now," Turner said. "I will run for the Senate, and I will run to win."

Running against Gillibrand — a popular and deep-pocketed Democratic incumbent — will be no easy task. Gillibrand won a 2010 special election with almost 30 points, and the state elects mostly Democrats in statewide races.

Gillibrand has more than $8.1 million in her campaign war chest. Turner has some ability to self-fund, which could help in New York’s expensive media market. His House account, which can be transferred to a Senate campaign, has $72,600 cash on hand but $65,500 in debt, according to Federal Election Commission records.

“In a very short time, Senator Gillibrand has developed a record of extraordinary accomplishment in the Senate fighting for New York families. Bob Turner is a former Rush Limbaugh producer turned Congressman who is at best a C-list candidate and will struggle to win over New Yorkers thanks to his partisan, far right voting record,” Democratic Senatorial Campaign Committee spokesman Matt Cantor said.

Senate Republicans don't see Gillibrand's seat as a pickup opportunity worthy of investing major resources, so Turner is likely to find himself mostly on his own if he wins the GOP primary.

Republicans had looked to Marc Cenedella — a businessman who could self-fund his campaign — but Cenedella dropped out after blog posts about sex and drugs were discovered on his website.

— This story was updated at 1:52 p.m.