Story highlights The Florida senator has tried to avoid antagonizing the brash Republican front-runner.

"Senator Marco "amnesty" Rubio, who has worst voting record in Senate, just hit me on national security-but I said don't go into Iraq. VISION," Trump tweeted

Washington (CNN) Donald Trump appears to have a new target: Marco Rubio.

The Florida senator has tried to avoid antagonizing the brash Republican front-runner, but on Tuesday evening Rubio finally landed in Trump's crosshairs.

"Senator Marco 'amnesty' Rubio, who has worst voting record in Senate, just hit me on national security - but I said don't go into Iraq. VISION," Trump tweeted.

Senator Marco "amnesty" Rubio, who has worst voting record in Senate, just hit me on national security-but I said don't go into Iraq. VISION — Donald J. Trump (@realDonaldTrump) September 23, 2015

Trump has a tendency to attack Republicans on the rise -- from GOP presidential rivals Jeb Bush to Carly Fiorina -- and the latest CNN/ORC poll shows an ascendent Rubio on the heels of his widely praised debate performance.

Earlier on Tuesday, Rubio suggested in an interview on Fox News that Trump was not ready to serve as commander-in-chief given Trump's sparse foreign policy knowledge.

Read More