Sen. Marco RubioMarco RubioElection hacking fears turn heat on Homeland Security Will Republicans stand up to the NRA's insurrection rhetoric? The Hill's Whip List: Senate ObamaCare repeal bill MORE (R-Fla.) on Tuesday backed freshman Rep. Tom CottonTom CottonCotton: US policy should be regime change in Iran Only Congress can enable drone technology to reach its full potential Senate Dem offers patent reform bill MORE (R-Ark.) for the Senate in his first endorsement of the 2014 cycle.

The endorsement comes with a twist, as Cotton is a strident opponent of the bipartisan immigration bill that Rubio helped pass through the Senate.

Rubio said Cotton would stick to his guns if elected to the Senate from Arkansas.

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"Once elected, we can be confident that Tom will be another conservative friend in Washington who will ensure that our children and grandchildren inherit an exceptional America from this generation," Rubio said in an email from his leadership PAC.

"He won't stand down when it comes to repealing ObamaCare, fighting to lower our runaway debt, and turning back the tide of big government that has taken over Washington in recent years."

Rubio and Cotton have similar political profiles.

Both are staunch fiscal conservatives bouyed by the Tea Party movement, and have been embraced by Washington's GOP establishment.

The two men also have hawkish views on foreign policy that are at odds with the libertarian streak that has taken hold in the GOP.

Cotton is running against Sen. Mark PryorMark PryorMedicaid rollback looms for GOP senators in 2020 Cotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm MORE (D-Ark.) in a must-win race for Senate Republicans if they hope to regain control of the upper chamber.