Marco RubioMarco Antonio RubioHow a nice-guy South Dakota senator fell into a Trump storm Republicans threaten floor takeover if Democrats weaken filibuster  Democrats must close the perception gap MORE regrets his personal attacks against his GOP competitor for the White House Donald TrumpDonald TrumpClyburn says he's worried about losing House, 'losing this democracy' Sinema reignites 2024 primary chatter amid filibuster fight  Why not a Manchin-DeSantis ticket for 2024? MORE, he told MSNBC Wednesday. 

"In terms of things that have to do with personal stuff, yeah, at the end of the day it's not something I'm entirely proud of," Rubio told the network in a town hall on Wednesday night. 
 
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"My kids were embarrassed by it, and if I had to do it again I wouldn't." 

Rubio had previously shied away from direct confrontation with Trump, but he burst out of the gate in the last debate before Super Tuesday by emptying the opposition research file against Trump.
 
The next morning, he bashed the billionaire as a "con artist" on television and days later poked fun at Trump's hands for being small.

"You know what they say about men with small hands?" Rubio said at a Feb. 26 rally. "You can’t trust them.” 

Despite the more aggressive tack, the Florida senator hasn't gained traction in the GOP nomination fight, falling hundreds of delegates behind Trump and Ted CruzRafael (Ted) Edward CruzOvernight Energy & Environment — Lummis holds up Biden EPA picks Equilibrium/Sustainability — Bald eagle comeback impacted by lead poison The Hill's Morning Report: Biden takes it on the chin MORE. His campaign has pinned all of its hopes on next week's Florida primary. 
 
At the same time,he told host Chuck Todd, "he needed to be stood up to."
 
Rubio also told MSNBC that he wouldn't be anyone's running mate -- including Trump's -- if asked. "I'm running for president."