NRA hopes to influence three key Senate races

The National Rifle Association will weigh in on three of this year's key Senate races with a multimillion dollar ad buy beginning Wednesday.

The NRA effort is aimed at boosting Republican Senate challengers in Arkansas, Colorado and North Carolina - the outcomes of which could likely determine which party controls the chamber.

The group's campaign is expected to top $4 million in these states, spokesman Andrew Arulanandam confirmed to CNN. It will spend $1.4 million to boost North Carolina House Speaker Thom Tillis, who is running against incumbent Democrat Sen. Kay Hagan.

"Our Second Amendment rights are under attack by the Obama Administration, and we need leaders like Thom Tillis in the Senate to fight back," states the ad.