The main super PACs supporting Ted Cruz are making a late push to give him a boost before Super Tuesday, launching a multimillion-dollar ad buy aimed at the mostly Southern states that are set to vote March 1.

The Keep the Promise super PACs announced Friday they are investing $2.4 million in the effort, which includes digital, radio and TV advertising across nine states. The largest part of the buy is going toward digital advertising, which the groups say will be targeted at primary voters in Texas, Oklahoma, Arkansas, Alaska, Tennessee, Alabama, Georgia and Minnesota.

The TV spending will total more than $990,000 in Georgia, Alabama, Tennessee, Arkansas and Oklahoma, according to Keep the Promise. It said its radio will amount to over $393,500 in Alabama, Arkansas, Georgia, Oklahoma, Tennessee, Texas and Virginia.

Both the TV and radio ads are previously released spots that play up Cruz's conservative credentials, especially when it comes to picking Supreme Court justices. The TV ads will run Saturday through Tuesday, according to Keep the Promise.

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"On Super Tuesday, voters can both send a message to Washington AND send a serious, proven conservative to the White House by voting for Cruz," Kellyanne Conway, president of Keep the Promise, said in a statement. 

The super PAC support arrives as Super Tuesday appears increasingly high stakes for Cruz, who has called it "the single most important day in this presidential election." A Bloomberg Politics poll released Thursday suggested Cruz could use the help, showing him in a tie for second place with Rubio in the seven Southern states set to vote Tuesday. Trump had a double-digit lead on both Cruz and Rubio. 

The digital and radio advertising in Texas appears to be the first serious paid effort to shore up Cruz's support at home, where he is favored to win but faces a credible threat in Trump.