MANCHESTER, N.H. -- Julian Castro has a message for President Trump.

The White House hopeful, at his first campaign stop in New Hampshire since declaring his candidacy for the Democratic presidential nomination, said that if he’s elected, Trump shouldn’t expect a pardon for any possible misdeeds that could come to light in coming months.

"I think that the next president is going to … make a decision like this about the president because one of those investigations, whether it's the Mueller investigation or it's in the Southern District of New York, is going to present the issue of punishment. That's what I believe," Castro said Tuesday night at a jam-packed tea café in this small city near the Maine border.

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The comments, from one of several longshot candidates entering what is likely to be a historically crowded field, highlight how the Russia probe and the prospect of Democrats someday delivering Trump’s comeuppance – whether in the form of impeachment or, in Castro’s case, the denial of a pardon – have factored into their campaigns, first in the midterms and now heading into 2020.

Castro, in his pardon remarks, was entertaining a scenario posed to him by a Democratic activist who asked whether he would use President Gerald Ford’s pardon of former President Richard Nixon in the wake of the Watergate scandal in the 1970s as a guide – in the event he is president and Trump is facing charges. Ford was criticized at the time, though many Americans felt he made the right move in helping the country move past the crisis.

"I would not be inclined to issue a pardon, because I don't think that anybody should be above the law," Castro, the former San Antonio mayor who later served as housing secretary under President Barack Obama, said to cheers and applause from the Democratic activists gathered at the café.

Trump has repeatedly denied there was any collusion between his presidential campaign and Russia to influence the results of the 2016 election, which is a focus of Special Counsel Robert Mueller’s investigation.

The president has also downplayed his role in hush-money payments made during the 2016 campaign to multiple women who allege they had affairs with Trump years earlier.

Emboldened by recent reports about the extent of the FBI’s initial Russia investigation, Trump has ramped up accusations that the bureau was out to get him. “They got caught spying on my campaign and then called it an investigation. Bad!” he tweeted earlier this week.

Castro was in New Hampshire – the state that traditionally holds the first primary in the race for the White House – for the first time since announcing his candidacy on Saturday in his native Texas.

He called for “new leadership in Washington D.C.,” saying, “We need new energy, we need a new vision, and we need somebody in the White House who is going to uphold the values of this country.”

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Both in his speech in Somersworth and in an address Wednesday morning at “Politics and Eggs” at the New Hampshire Institute of Politics – a must-stop for White House hopefuls – Castro spelled out his progressive proposals, which included “universal pre-K education so that every kid can start off with a good education.”

He also advocated for Medicare for all, investments in clean water and infrastructure and addressing the nation’s justice system “to make sure that equality under the law truly exists no matter what your background is.”

Castro said he’d make a push for affordable housing a major part of his campaign, called for investing in the newly proposed Green New Deal and touted that “my first executive order as president will be to recommit the United States to the Paris Climate Agreement.”

Asked by the pro-business and academic crowd on Wednesday how he’d pay for all his proposals, Castro admitted that “I know that’s not going to be an easy task.”

He added that he would put forward plans during his White House bid on how he’d pay for his big-government pitches.

Pressed later by reporters, Castro explained that he would try to increase revenues and shave costs by “reforming our tax system and also reforming the way we do health care.”

“You’re going to have to reform our tax code so that it’s more fair. So that people at the top pay their fair share, so that wealthy corporations pay their fair share, that you don’t have things like Amazon getting billions of dollars of tax abatements,” he added.

The Republican National Committee took aim at Castro ahead of his visit.

"Democrat lightweight Julian Castro is making his way through New Hampshire to sell his big-government agenda of higher taxes and socialized healthcare,” RNC spokeswoman Mandi Merritt said.

“Castro’s visit to the Granite State amounts to nothing more than a mandatory campaign stop for an ego-driven politician that cares more about advancing his career than helping New Hampshire families.”

Castro also highlighted the issue of illegal immigration, taking aim at the president.

“We need to stamp out the narrow-minded fear and paranoia and scapegoating and division that’s been a part of this administration,” he stressed in Somersworth.

“We can have border security, but we need to do the smart way, investing in personnel, investing in technology. Not building a dumb wall and not putting babies in cages. Donald Trump has violated some of the most sacred values and ideals of this nation,” Castro charged.

And in an interview with Fox News, Castro criticized Trump’s work ethic.

“I wonder how folks feel that this president in a given week often works less than the average part-time worker,” he charged. “You have a president of the United States whose first meeting after watching TV all morning is at 11 a.m.”

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Castro arrived in New Hampshire as Sen. Kirsten Gillibrand of New York went on late night TV to announce the formation of an exploratory committee.

Asked how he could compete with candidates like Gillibrand or Sen. Elizabeth Warren of Massachusetts who will out-fundraise him or with potential rivals like former Vice President Joe Biden and Sen. Bernie Sanders of Vermont, who have much greater name recognition, Castro told Fox News: “I’m going to have to work hard. I’m working hard right now. We’re going to have to be scrappy as a campaign.”

But he added that “I’m under no illusion that I’m a front-runner in this campaign.”

“For a candidate like me, that doesn’t start off with the biggest name ID or the biggest bank account, or the biggest platform right now, I appreciate that so many people in New Hampshire are willing to make the effort to come here today at 8 a.m. in the morning to listen to a candidate who is running,” he added on Wednesday.

Asked if Iowa and New Hampshire – the states that vote first in the caucus and primary calendar – are not diverse enough, Castro answered “do I wish that in the first two states, we had more diversity in those states? Yeah, I do.”

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But he added that what “I do appreciate about Iowa and New Hampshire is that people take politics and policy very seriously, and these are relatively small states as far as states go, so that you can actually meet people one on one and get to know them.”