SOUTHAMPTON, N.Y. – Hillary Clinton plans to stress her support for American exceptionalism during a speech in the battleground state of Ohio, while arguing that Donald Trump has rejected the concept.

Clinton’s midday address at the American Legion’s annual convention in Cincinnati Wednesday comes as Trump plans a last-minute trip to Mexico in advance of a long-awaited speech on immigration. A Clinton campaign official said the Democratic nominee plans to use her first public event in days to portray her Republican opponent as a questionable leader who would “walk away from our allies, undermine our values, insult our military – and has explicitly rejected the idea of American exceptionalism.”

In contrast, the official said Clinton “will make the case for American exceptionalism and call for maintaining America’s military and diplomatic leadership in the world.”

American exceptionalism refers to the country’s elevated standing and leadership in the world. Donald Trump has pledged to “Make America Great Again” and restore the country to a time when, in his view, the U.S. was more prosperous and full of opportunity than now. Democrats, including President Barack Obama, insist America is already great, or “exceptional.”

To bolster her argument, Clinton will talk about her experience, including serving on the Senate Armed Services Committee and as secretary of state. She will also emphasize the growing list of Republicans who have backed her campaign.

A campaign official said that in advance of her Wednesday speech, another leading Republican would back the campaign. James Clad, former Deputy Assistant Secretary of Defense under President George W. Bush, will announce his support for Clinton, following a slew of GOP endorsements. In a statement, Clad will say that “giving an incoherent amateur the keys to the White House this November will doom us to second or third-class status.”

Clinton’s remarks come on the same day her Republican opponent is set to deliver a long-awaited speech on immigration where he is expected to provide more clarity on his primary pledge to deport all of the estimated 11 million people living in the country illegally. While Trump had said during the primary that he intended to accomplish that goal with the help of a “deportation force,” in recent weeks he has suggested in closed-door meetings with Hispanic activists that he might be open to re-considering. He and his aides have spent the last week-and-a-half offering mixed signals.

Trump is scheduled to speak in Arizona in the evening. Trump’s campaign said Tuesday night that he will make a surprise trip to Mexico on Wednesday to meet with Mexican President Enrique Pena Nieto. The Washington Post first reported the planned trip.

Responding to Trump’s Mexico plans, Clinton communications director Jennifer Palmieri said in a statement that “what ultimately matters is what Donald Trump says to voters in Arizona, not Mexico, and whether he remains committed to the splitting up of families and deportation of millions.”

Clinton’s campaign says she has also been invited by Nieto to make a visit and that the two will talk again at “the appropriate time.”

Clinton’s speech in Ohio comes after several days of big-ticket private fundraisers in the Hamptons, a wealthy community on New York’s Long Island, where she collected millions at waterfront mansions in preparation for the fall campaign. The fundraising swing concluded in style Tuesday night, with an event featuring performances from Jimmy Buffett, Jon Bon Jovi and Paul McCartney.

Though many national and state polls show Clinton with an edge, she has been stressing that the campaign must not take anything for granted. At a fundraiser on Monday she told supporters she was “running against someone who will say or do anything. And who knows what that might be.”