'Significant sign': Reporter floored as first domino falls in Trump's bid to upend Indiana

CNN commentators flagged the loss of an established Republican congressman to a Trump-backed contender during primaries on Tuesday as a "significant sign" of who's the boss in the GOP.

The race for an Indiana state senate seat was called in favor of Blake Fiechter on Tuesday. Trump threw his support behind Fiechter, a real estate agent, to beat incumbent Sen. Travis Holman after he joined with Democrats and other Republicans to vote down a measure that would have redrawn Indiana's congressional maps in favor of the GOP.

"These elections are a major test for the President's power over his own party," explained CNN anchor Erin Burnett. "Trump putting an unprecedented amount of money in for the GOP to fight other Republicans, the ones he's trying to get rid of."

Fiechter had a 20-point margin of victory when CNN called the race in his favor late Tuesday. Burnett and national affairs correspondent Jeff Zeleny described it as a "significant" victory for Trump's side.

"The defeat of Sen. Travis Holman is significant because he is the third-ranking Republican in the Indiana state senate," Zeleny explained. He added that it doesn't bode well for others facing Trump's ire, as Holman was "effectively the leader of these seven senators who are on the ballot today, so certainly a convincing win there."

Holman had been in the Indiana state senate since 2008, "so this is significant," Zeleny added, with Burnett agreeing, "yeah, it's a significant sign."

"What this really is going to show is if the Trump coalition is going to respond to a massive advertising campaign," Zeleny said. "We have not seen anything like this."

Zeleny explained that Holman voted against redistricting because "he thought it was the wrong thing to do," and now, "he's going to be effectively thrown out of office."