Democratic vice presidential candidate Tim Kaine questions if Donald Trump would stand up to Russia if that government hacked into the U.S. political system in an attempt to influence the election. (Reuters)

ERIE, Pa. — Democratic vice-presidential candidate Tim Kaine on Tuesday questioned whether a President Donald Trump would stand up to a Russian cyberattack aimed at destabilizing U.S. elections, citing questions about the Republican’s foreign business dealings and the “pro-Kremlin” views of some of his associates.

“He’s encouraged Russia already to get in and screw around with our elections,” Kaine said during a rally here. “Donald Trump poses a unique threat to American democracy, unlike anything we’ve seen in any presidential election in my lifetime.”

Kaine’s pointed questions about Trump’s coziness with Russia came amid a sweeping attack on the Republican candidate, whom Kaine lambasted for not making key records public related to his health, personal finances and overseas business interests.

Collectively, the lack of disclosure, the senator from Virginia said, leaves many questions unanswered about Trump that should deeply trouble voters.

“A candidate who is on the up and up has no problem giving you the facts,” Kaine said. “Donald Trump thus far has utterly failed to answer basic questions that voters have a right to know.”

Representatives of the Trump campaign did not immediately respond to Kaine’s accusations.

In discussing Russia, Kaine cited Trump’s call last month for Russia to help find missing emails of Democratic presidential candidate Hillary Clinton, just as news had broken about the apparent hacking of Democratic National Committee accounts.

Kaine also noted that Trump has yet to fully disclose the extent of his business ties in Russia. He also cited the earlier political work of Trump’s former campaign chairman, Paul Manafort, on behalf of pro-Russian figures.

Kaine said Trump adviser, retired Army lieutenant general Michael T. Flynn, has appeared on a Russian “propaganda channel” on television. And Kaine said that the new chief executive of Trump’s campaign, Stephen K. Bannon, has run a website, Breitbart News, with “pro-Kremlin positions.”

“Just imagine if Russia were to engage in a cyberattack to destabilize the American electoral process, as it has done with other nations,” Kaine said. “Would President Trump stand up to them? Well, you know, we actually know the answer to that one already because Trump has publicly encouraged Russia to commit espionage and hack his political rivals.”

As he has in previous campaign stops, Kaine continued to needle Trump about not voluntarily releasing his tax returns, as Clinton and Kaine have done. And Kaine said that Trump, who has bragged about his use of debt as an instrument in his real estate and other business dealings, needs to be more forthcoming about his obligations, including to foreign entities.

“When you’re running for president, American voters have the right to know who might have you on the hook,” Kaine said. “No one has ever entered the White House owing so much money to so many institutions all over the planet.”

In recent weeks, Trump and his backers have sought to raise questions about Clinton’s health, suggesting without specific evidence that she is attempting to hide medical conditions that could affect her ability to carry out the duties of president.

During Tuesday’s remarks, Kaine said it was Trump who needs to be more forthcoming about his health.

Kaine mocked Trump for a hastily written doctor’s letter attesting to his well-being in December that has come under renewed scrutiny. And Kaine suggested that Clinton’s stamina is clear from her time spent on the campaign trail.

“I have been on the trail for five weeks with Hillary, and I can barely keep up with her,” Kaine said.

During a later appearance in Lancaster, Pa., Kaine also mocked the contention in the letter that Trump would be the healthiest president ever to enter office.

“I’d like to see him play basketball against the current president," Kaine said

Kaine’s appearance here was part of a two-day swing through Pennsylvania. While Trump has sought to put the state in play, a Monmouth University poll released Tuesday showed Clinton beating him in the state, 48 percent to 40 percent. Another 6 percent voiced support for Libertarian Gary Johnson, while 1 percent were backing Jill Stein of the Green Party.