Donald Trump was once again at the center of a firestorm Wednesday, this time over controversial comments interpreted by some as a threat of violence against presidential campaign rival Hillary Clinton. Trump's intended message was not immediately clear, but lawmakers, former national security officials and other critics expressed concern that he had advocated, possibly in jest, that Clinton or her Supreme Court nominees could be shot. "Hillary wants to essentially abolish the Second Amendment," Trump told a rally in Wilmington, North Carolina, referring to the US Constitution's clause that enshrines "the right to bear arms." "If she gets to pick her judges, nothing you can do, folks," Trump said. "Although the Second Amendment people — maybe there is, I don't know," he said, in remarks that some deemed his most explosive and most offensive to date. Trump earlier appeared more focused on delivering his typical campaign stump speech about Clinton, telling supporters she would represent four more years of President Barack Obama, "but maybe worse," and sparring with her over policy. "I gave a massive tax decrease yesterday," Trump said, referring to economic plans he unveiled Monday. "Clinton, she's going to double up your taxes." But then Trump drew attention away from his message with his "Second Amendment" remarks. It was the latest in a long string of Trump trip-ups — including his clash with the parents of a Muslim American soldier killed in action — that have marred his campaign since he officially won the nomination last month, prompting several Republicans to reject his candidacy. Clinton's campaign decried Trump's "dangerous" language and demanded in a statement that presidential hopefuls "not suggest violence in any way." Trump's team fired back to say the 70-year-old Manhattan billionaire simply meant that gun rights advocates were a powerful voting force. "Second Amendment people have amazing spirit and are tremendously unified, which gives them great political power," senior Trump communications advisor Jason Miller said. The National Rifle Association, America's largest pro-gun lobby, put forth that Trump was correct in saying it would be hard to protect the Second Amendment if Clinton appoints new justices. "But there IS something we will do on #ElectionDay: Show up and vote for the #2A!" the group posted on Twitter. Trump is struggling to transition from his strong grassroots primary performance to a more mature head-to-head battle with Clinton. He suffers from sinking poll numbers, including a Quinnipiac University survey released Tuesday that shows him trailing Clinton in crucial battleground states Ohio and Pennsylvania, and virtually tied in Florida. Democratic lawmakers expressed shock about Trump's comments. "In this clip, Trump's either calling for an armed revolt or the assassination of his opponent. Despicable," Democratic congressman David Cicilline posted on Twitter along with footage of Trump's remarks. The Secret Service — which is tasked with protecting both Trump and Clinton — said it "is aware of the comments," but did not say whether they merited an investigation, which some Democratic lawmakers have called for. At a later rally in Fayetteville, North Carolina Trump avoided addressing his controversial comments. But the supporter who introduced him, former New York mayor Rudy Giuliani, sought to clarify the remarks, insisting Trump had not aimed to incite violence. "What he meant by that was, you have the power to vote against her," Giuliani said. Trump's repeated stumbles and divisive rhetoric have angered Republican Party grandees. Former CIA director Michael Hayden blasted the "Second Amendment" comments. "It suggests either a very bad-taste reference to political assassination and an attempt at humor, or an incredible insensitivity," he told CNN. Hayden was among 50 former senior Republican national security officials who warned in an open letter Monday that if Trump were elected he would be "the most reckless president in American history." Influential Republican US Senator Susan Collins piled in, saying the nominee was "unworthy" of America's highest elective office and would not receive her support. Joe Scarborough, a former member of the House of Representatives and now a television host, wrote in the Washington Post that Trump's Second Amendment remark was the final straw. "What else could Trump do that would be worse than implying the positive impact of a political assassination?" the former US lawmaker wrote. "The Republican Party needs to start examining quickly their options for removing the Republican nominee," Scarborough said.