(CNN) Donald Trump and his surrogates amplified their argument over the weekend that the election is "rigged," leaving the Republican nominee more isolated as top members of the GOP -- including his own running mate -- declared their faith in the political system.

Trump opened Sunday with a series of tweets sowing doubt about the legitimacy of the election.

"The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places - SAD"

But Trump's own vice presidential nominee, Indiana Gov. Mike Pence, disagreed during an interview on NBC's "Meet the Press," saying he will accept the Election Day results.

"We will absolutely accept the result of the election," he said. "Look, the American people will speak in an election that will culminate on November the 8. But the American people are tired of the obvious bias in the national media. That's where the sense of a rigged election goes here, Chuck."

That stood in contrast to Trump's top surrogates. Former New York City Mayor Rudy Giuliani claimed that Democrats could steal a close election by having dead people vote in inner cities.

"I'm sorry, dead people generally vote for Democrats rather than Republicans," Giuliani told CNN's Jake Tapper on "State of the Union." "You want me to (say) that I think the election in Philadelphia and Chicago is going to be fair? I would have to be a moron to say that."

And Newt Gingrich, the former House speaker, on ABC's "This Week" urged Trump voters to monitor polling stations.

"I remember when Richard Nixon had the election stolen in 1960, and no serious historian doubts that Illinois and Texas were stolen. So to suggest that, we have, you don't have theft in Philadelphia is to deny reality," Gingrich said.

The intensity surrounding the election is building in the final weeks of the race. In the evening, Trump -- without evidence -- blamed the firebombing of a North Carolina local GOP office on supporters of Hillary Clinton.

"Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning @NCGOP," Trump tweeted Sunday night.

For its part, the Clinton campaign quickly tweeted a note of sympathy.

"The attack on the Orange County HQ @NCGOP office is horrific and unacceptable. Very grateful that everyone is safe."

The North Carolina Republican Party tweeted its appreciation in response.

"Thank you for your thoughts & prayers, Sec. @HillaryClinton."

Intensifying Trump criticism of Clinton

The "rigged election" allegations by Trump and his top lieutenants came after an event Saturday in New Hampshire in which the candidate refuted allegations he groped and kissed women without their consent as "total lies."

Trump also argued, once again, that Democratic rival Hillary Clinton "should have been prosecuted" and "be in jail" for her improper use of a private email server at the State Department. She escaped prosecution, Trump alleged, because of collusion between the Clintons and the Department of Justice.

He also used that claim earlier Saturday to fundraise.

"Folks, there's never been a situation like this in the history of our country," Trump said at a campaign rally here.

Trump also sought to discredit the women who have accused him of sexual assault in recent days, calling one a "crazy woman" and pointing to a statement from the cousin of another accuser.

John Barry, the cousin of Summer Zervos, a former "Apprentice" contestant who on Friday accused Trump of having groped her, had released a statement Friday evening through the Trump campaign alleging that Zervos had "praised" Trump and supported Trump's presidential bid until recently.

Zervos' attorney, Gloria Allred, in turn called Barry "a huge Trump supporter."

Trump argued that other allegations are "total lies" and have "already been proven so false."

But Trump primarily raised the allegations to argue again that the media outlets reporting on the allegations -- many of which describe actions Trump bragged about in a 2005 conversation that surfaced last week -- are doing so to sink his campaign.

"Remember this, it's a rigged election because you have phony people coming up with phony allegations with no witnesses whatsoever," Trump said. "The election is being rigged by corrupt media pushing completely false allegations and outright lies in an effort to elect her (Clinton) president."

A sitting senator, Jeff Sessions of Alabama, added his voice to Trump's attack in remarks before the GOP nominee took the stage, saying "they will not succeed" in manipulating the election.

Asked for comment in light of Trump's remarks, the office of Republican House Speaker Paul Ryan vouched for the integrity of the US electoral process Saturday afternoon.

"Our democracy relies on confidence in election results, and the speaker is fully confident the states will carry out this election with integrity," said AshLee Strong, a spokeswoman for Ryan.

Fundraising off threat

Trump's remarks came after his campaign pushed out a plea for donations to supporters by pointing to his vow to investigate and prosecute Clinton if elected, a threat that is unprecedented in modern US political history. Trump even issued the threat to Clinton at the last presidential debate.

"As I promised on Sunday, if elected I will appoint a special prosecutor to look into Crooked Hillary's emails and get the answers the American people deserve," Trump says in the email.

He again cited his argument that Clinton is the "ultimate career politician, enriching herself off of the rigged system for decades while getting NOTHING accomplished."

When Trump brought up the threat at Sunday's debate, Clinton responded, "It's just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country."

To which Trump replied, "Because you'd be in jail."

The Department of Justice, acting on an FBI recommendation, declined to press criminal charges against Clinton regarding the matter over the summer.

'Rigged' claims

Earlier Saturday, Trump continued to claim that the election is "rigged" against him, citing the sexual assault charges that have embroiled his campaign.

"100% fabricated and made-up charges, pushed strongly by the media and the Clinton Campaign, may poison the minds of the American Voter. FIX!" Trump tweeted.

He followed up: "This election is being rigged by the media pushing false and unsubstantiated charges, and outright lies, in order to elect Crooked Hillary!"

And again: "Hillary Clinton should have been prosecuted and should be in jail. Instead she is running for president in what looks like a rigged election."

Later in the afternoon, he added: "Nothing ever happened with any of these women. Totally made up nonsense to steal the election. Nobody has more respect for women than me!"

Trump has warned of a "rigged" election for months. He said in North Carolina Friday that "the whole thing is one big fix" and, railing against the sexual assault allegations, said he was the "victim" of a "political smear campaign."

But his comments come as his campaign has urged him to focus on issues and Clinton, particularly in the wake of politically damaging WikiLeaks releases, with just over three weeks to go before Election Day. Trump's poll numbers have been declining since the first presidential debate late last month, and his polling troubles accelerated with the surfacing of a 2005 tape last week in which Trump bragged about being able to grope women and get away with it.