Sen. Marco Rubio (R-Fla.) on Tuesday backed freshman Rep. Tom Cotton (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.
"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 Pryor (D-Ark.) in a must-win race for Senate Republicans if they hope to regain control of the upper chamber.