In just three weeks, outside groups have spent more than $1 million in Houston's heavyweight Republican primary battle between former Navy SEAL Dan Crenshaw and state legislator Kevin Roberts.

On Thursday, a group calling itself Conservative Results Matter spent $84,000 for radio ads opposing Crenshaw. That comes three days after a group called the With Honor Fund put $32,290 into mailers supporting Crenshaw, and another group calling itself American Patriots PAC poured $121,000 into ads against Republican Kevin Roberts.

It's just the latest spending from outside groups who have spent $1.2 million in the race since April 20, according to the latest filings with the Federal Election Commission.

The outside groups -- often known as Super PACs -- can raise unlimited donations from donors, but are prevented from directly coordinating with campaigns. Often they are created before elections so their donors are not fully identified after an election.

Here's an ad American Patriots PAC released in support of Crenshaw.

Roberts and Crenshaw are battling in a GOP primary runoff on May 22. Early voting starts Monday. The winner will advance to take on Democrat Todd Litton in November.

The race is for the 2nd Congressional District, which includes parts of West Houston, wraps around to the northern Harris County line with Montgomery County and whips east to pick up Humble and Atascocita.

Here's a breakdown of how much outside groups have spent in the 2nd Congressional District

American Patriots PAC - $233,504

Who They Are: The chairman of the group is Dan Conston, a D.C. political consultant who has a history of working for outside groups like the American Action Network and Congressional Leadership Fund.

When they were created: Feb. 6, 2018.

Who is funding the PAC: So far only one donor has been made public, Edward J. Guinn, a Montgomery County medical consultant who has given $105,000 to the group.

Who they are backing: Crenshaw.

https://www.americanpatriotpac.org/

Conservative Results Matter - $590,000

Who They Are: The Austin-area based group has only identified its treasurer as Deanna Hayes, who runs a political financing company called Grand Slam Finance in Austin. The PAC's address is a shopping plaza in Cedar Park, just north of Austin.

When they were created: March 29, 2018.

Who is funding the PAC: Unknown. The group has not had to list any of its donors yet.

Who they are backing: Roberts.

http://conservativeresultsmatter.com/

With Honor Fund Inc - $550,417

Who they are: An Alexandria, Va. based group created in 2017 aimed at electing more veterans to Congress. The group was co-founded by former presidential campaign advisor David Gergen and Rye Barcott, a retired Marine.

When they were created: Dec. 25, 2017.

Who is funding the PAC: Leslie and Abigail Wexner of Ohio, the founders of L Brand, which includes Victoria Secrets, have donated $2.8 million to the group. Miguel and Jacklyn Bezos of Washington State (parents of Amazon CEO Jeff Bezos) have given just under $1 million to the group.

Who they are backing: Crenshaw.

https://www.withhonor.org/

Defenders of Freedom and Security - $6,720

Who they are: A California-based PAC that has also supported five other Republicans running for Congress this year, including U.S. Rep. Karen Handel of Georgia and Michigan Republican Senate candidate John James.

When they were created: Oct. 24, 2016.

Who is funding the PAC: The group has raised just $124,000 since the start of 2017, and mostly from small donors, none of which has given more than $2,000 to the group.

Who they are backing: Crenshaw.

https://www.defendersoffreedomandsecurity.com/

Texas Tea Party Patriots PAC - $17,635

Who They are: The Montgomery County group founded by Suzanne Guggenheim and Julie Turner.

When they were created: 2009

Who they are backing: Crenshaw.

https://www.texaspatriotspac.com/

Jeremy Wallace writes about state politics and government for the Chronicle. Follow him on Twitter at @JeremySWallace.