Story highlights Cruz called close results in a special House election a "warning sign"

The race took place in a solidly conservative district in Kansas

Cruz attributed the narrow margin to an "energized" Democratic base

Washington (CNN) The surprisingly close results of Tuesday's special election for a House seat in deep-red Kansas should serve as "a warning sign" to the GOP, Sen. Ted Cruz said Wednesday.

The contest showed the massive shift in the electorate since voters elected Donald Trump President in November. He had carried the Kansas district by 27 percentage points but on Tuesday, Republican Ron Estes only bested Democrat Jim Thompson for the seat previously represented by new CIA Director Mike Pompeo by 7 points.

Though it's far too early to know whether those Democratic gains will hold through the 2018 midterm elections, Kansas was an ominous sign for the GOP ahead of a much closer Georgia 6th District special election next week in Atlanta's northern suburbs -- as well as other upcoming special elections in Montana and South Carolina.

"The radical left is filled with fury right now," Cruz, R-Texas, told radio host Chris Salcedo. "I mean, they're blind with rage. As a result, they're energized -- they will crawl over broken glass. And we knew they would show up, and they did show up."

Cruz, who made a Monday trip to Wichita, told the radio host that he stumped for GOP candidate Ron Estes because "the numbers were looking close" -- and that his party should view the narrow margin as a red flag.

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