Republican vice-presidential nominee Gov. Mike Pence on Sunday suggested a federal investigation into whether Hillary Clinton, during her tenure as secretary of state, provided political favors to foreign donors to her family’s Clinton Foundation, saying “the American people have a right to know.”

The Indiana governor argued that emails made public last week suggested such a connection between State Department officials and major foreign donors to the foundation but acknowledged that Clinton’s involvement remains unclear.

“It looks that way more and more every day,” Pence said. “That's what we need to find out. … This is exactly the kind of pay to play politics the American people are sick and tired of. It is just one more example of the way I do believe that the Clintons have been operating over the last 30 years.”

He also argued that some FBI officials wanted an investigation, but President Obama's Department of Justice “apparently has shut that down.”

Missouri Democratic Sen. Claire McCaskill, a strong Clinton supporter, said later on “Fox News Sunday” that only two emails were released and that they provided “no evidence” that any of Clinton’s State Department decisions were influenced by foundation activities.

However, McCaskill acknowledged that the department under Clinton putting foundation donor Rajiv K. Fernando on a sensitive government intelligence advisory board without him having the requisite experience was “not such a good idea.”

Pence on Sunday was again forced to try to make clear whether GOP presidential nominee Donald Trump was being sarcastic in claiming that Obama and Clinton -- his former secretary of state and now the Democratic presidential nominee -- co-founded the Islamic State terror group.

“He was being very serious,” Pence said. “And he was making a point that needs to be made, that there is no question that the failed policies of President Barack Obama and Secretary of State Hillary Clinton, in the wider Middle East, created a vacuum within Iraq in which ISIS was able to arise.”

Pence confirmed that Trump is scheduled to make a speech Monday in battleground state Ohio on the issue and vowed that Trump would “lay out his vision and his strategy for defeating radical Islamic terrorism.”

“Get ready,” said Pence, adding that Trump will announce “real specifics” about how, if elected, he would change U.S. policy and provide the kind of “broad-shouldered leadership” that would make the country safer.

McCaskill argued that Trump’s comments about who founded ISIS are “disrespectful” to the U.S. military, then attacked Trump, saying he and “his best buddy” Russian President Vladimir Putin “are the founder of ISIS, which probably would be more accurate.”