As President Trump left for Atlanta Wednesday to address a summit on drug addiction and the opioid crisis, it was subpoenas directed at his former top officials that evoked his ire.

Asked by a reporter on the White House South Lawn about a subpoena for former White House counsel Don McGahn, who told special counsel Robert Mueller's office that he ignored the president's order to fire Mueller, the president said his White House is fighting "all the subpoenas." Mr. Trump told the Washington Post on Tuesday that he is against any current or former White House officials testifying about the report before Congress.

"The subpoena is ridiculous" after the "witch hunt" is over, the president told reporters.

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"We're fighting all the subpoenas," the president added. "These aren't like impartial people. The Democrats are trying to win 2020. They're not going to win with the people that I see. And they're not gonna win against me. The only way they can maybe luck out, and I don't think that's gonna happen – it might make it even the opposite, that's what a lot of people are saying – the only way they can luck out is by constantly going after me on nonsense."

As Mr. Trump prepared to leave for Atlanta, it was illegal immigration and Mueller's investigation that were on the president's mind. The president spent part of his morning tweeting his frustrations with illegal border crossings, threatening to send "ARMED SOLDIERS" to the border after claiming Mexican troops pulled guns on American troops.

The commander-in-chief, despite his remarks claiming Mueller's report exonerates him completely, also tweeted his frustrations with the cost and scope of the investigation. If Democrats try to impeach him over the report's findings, the president said he'll take his case to the Supreme Court. But impeachment is a political tool, not a legal one, and he would have no recourse in the highest court of the land.

"The Mueller Report, despite being written by Angry Democrats and Trump Haters, and with unlimited money behind it ($35,000,000), didn't lay a glove on me. I DID NOTHING WRONG. If the partisan Dems ever tried to Impeach, I would first head to the U.S. Supreme Court," the president tweeted Wednesday morning.

Mr. Trump is heading to Atlanta with First Lady Melania Trump to address the Rx Drug Abuse and Heroin Summit. The president has vocally prioritized addressing the opioid crisis, although experts say the funding made available to address the crisis in the time he's been in office isn't nearly sufficient.