During a 2017 debate over whether Montenegro should be permitted to join the NATO alliance, the late Senator John McCain (R-AZ) accused Kentucky Senator Rand Paul (R) of “working for Vladimir Putin” after Paul objected to the resolution.
According to CNN, McCain blasted Paul on several occasions over his vote against the resolution:
Pointedly singling out the "gentleman from Kentucky," McCain said those who object "are now carrying out the desires and ambitions of Vladimir Putin."
When Paul formally objected, McCain reiterated his opinion.
"The senator from Kentucky is now working for Vladimir Putin," he said.
When McCain’s office was asked whether he believed he violated Senate Rule 19 — which states, "No senator in debate shall, directly or indirectly, by any form of words impute to another Senator or to other Senators any conduct or motive unworthy or unbecoming a Senator” — McCain’s spokeswoman said:
"Sen. McCain believes that the person who benefits the most from Congress' failure to ratify Montenegro's ascension to NATO is Vladimir Putin," Julie Tarallo, a McCain spokeswoman, told CNN. "The senators who support this treaty, and certainly the people of Montenegro, deserved an explanation from Sen. Paul."
Paul went on to visit the Kremlin in August 2018, and upon his return, the Republican senator asked President Donald Trump to lift sanctions on Russian lawmakers that they might travel to the U.S. for further talks.
Paul was also one of extremely few lawmakers to publicly support the president after Trump appeared to accept Putin’s denial of election interference during their meeting in Helsinki, Finland last year.