Story highlights The election is to replace Rep. Mike Pompeo, now the CIA director

Washington (CNN) Republicans have called in the cavalry ahead of a Tuesday special election for a House seat in deep-red Kansas.

Vice President Mike Pence recorded a robo-call backing the GOP candidate, Ron Estes. The National Republican Congressional Committee is spending nearly $100,000 on ads in the closing days. And Texas Sen. Ted Cruz -- who won the state's 2016 Republican presidential primary -- is headed there for a Monday afternoon event.

It all comes amid concerns that the Wichita-based 4th District -- vacated when former Rep. Mike Pompeo became President Donald Trump's CIA director -- has suddenly turned into a real race.

Republicans hope it won't forebode even worse news a week later, in a Georgia House contest where Democrat Jon Ossoff has raised more than $8 million, or later in a Montana House special election.

Here are five things to know ahead of Tuesday's special election:

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