If Rand Paul's goal was to get Donald Trump's attention, it seems that mission has been accomplished.
Monday night, hours after Paul held a conference call with reporters for the express purpose of calling out Trump as a "fake conservative," Trump took to Twitter to respond.
"Truly weird Senator Rand Paul of Kentucky reminds me of a spoiled brat without a properly functioning brain," Trump tweeted. "He was terrible at DEBATE!"
At last week's debate, Paul went after Trump from the opening moments, accusing the real estate developer of "hedging his bet" by refusing to rule out running as an independent.
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Since then, Paul has made attacking Trump a focus in remarks on the campaign trail and on Fox News Sunday.
Paul, Kentucky's junior senator, has faced a number of setbacks since entering the race for the Republican presidential nomination in April, and his new focus on Trump comes as polls show him losing support and two of his top allies were indicted last week.
In his responses Monday night, Trump seemed to know where to find one of Paul's soft spots, referencing Paul's efforts to get around a state law that prohibits him from running simultaneously for the presidency and the Senate next year.
"Why is @RandPaul allowed to take advantage of the people of Kentucky by running for Senator and Pres.," Trump tweeted. "Why should Kentucky be back up plan?"