Former congressman David Rivera (R-Fla.), who is under federal investigation, will make another run for Congress, he announced Thursday, a surprising decision that threatens to complicate the picture for Republicans in a Florida U.S. House district they are eagerly contesting.

"Today I announced my candidacy for the United States Congress in Florida's 26th Congressional District," Rivera said in a statement Thursday. "I'm running to ensure that our community has an effective representative in Congress who can work to deliver results and create jobs in South Florida. The current Congressman is a democrat who represents the failed economic policies of Barack Obama and Nancy Pelosi. It's time for a change."

He was unseated in Congress by Rep. Joe Garcia (D) in 2012. Rivera is under investigation by the federal government for potential ties to a campaign finance scheme involving a Democratic opponent of Garcia's who received unreported campaign cash. The Miami Herald, which has covered the matter extensively,  reported Thursday that when Rivera made his campaign announcement on Spanish-language television, he would not talk about the investigation.

Rivera's decsion puts him at odds with Miami-Dade School Board member Carlos Curbelo (R), who is already in the race against Garcia. Curbelo is a highly-touted recruit who was recently promoted to "Contender" in the National Republican Congressional Committee's "Young Guns" program for top challengers and open seat hopefuls. He's also backed by former Florida governor Jeb Bush (R).

"I just got the news and wanted to make sure that you heard it from me: David Rivera is going to run for Congress again, despite being under investigation by federal agencies for serious allegations," Curbelo wrote in a fundraising e-mail sent Thursday evening.