John Ratcliffe, in his campaign office in Heath, Texas, in March. (Kim Leeson/For The Washington Post)

John Ratcliffe became the first primary challenger in either party to unseat an incumbent Tuesday night -- and he scored a big victory.

Ratcliffe, 48, defeated incumbent Rep. Ralph Hall (R-Texas), the 91-year old, 18-term incumbent who is one of the last World War II veterans serving in Congress.

So who is Ratcliffe? Here's what you need to know:

He once hosted a fundraiser for Ralph Hall in his home.

Yup, but late last year Ratcliffe jumped into the race to defeat the incumbent congressman. He placed second to Hall in a March runoff and over the course of the runoff, has spent more than $500,000 of his own fortune, mostly on television advertisements.

Ratcliffe mostly avoided directly questioning Hall's age and fitness for office, but notice here how his campaign ads used subtle messages -- including his young daughters -- to emphasize that he would be part of a "new opportunity" and a "new generation" or the "next generation" of conservative leadership:


And here...

As U.S. attorney, Ratcliffe organized a sting operation that led to the arrest of more than 300 illegal immigrants in a single day.

Ratcliffe was already working on counterterrorism cases for the Justice Department when President George W. Bush appointed him U.S. attorney for the Eastern District of Texas -- a 43-county jurisdiction -- in 2007. The next year, Ratcliffe oversaw "Operation Plymouth Rock," a sting that led to the arrest of 300 undocumented immigrants who had committed identity theft and social security fraud in order to get jobs with Pilgrim's Pride, a food company owned by GOP donor Bo Pilgrim. Ratcliffe sought a $4.5 million penalty against the company.

Ratcliffe worked for John Ashcroft during the Bush administration and still works for him today.

Ashcroft, the former attorney general, runs a lucrative lobbying firm and a separate legal practice. Ratcliffe helps run the law firm's Dallas office with a focus on corporate law.

Ratcliffe might have served in Mitt Romney's administration.

He was one of a small handful of people who was hired by Romney's 2012 presidential campaign to begin working on a potential presidential transition in the months before Election Day. Working on a team led by Mike Leavitt, the former Utah governor, secretary of Health and Human Services and longtime Romney friend, Ratcliffe helped begin the vetting process for potential Cabinet secretaries and other senior government appointees.

Ratcliffe said in a March interview with The Washington Post that "conceivably" he would be working at the Justice Department right now if Romney were president.