Sen. John McCain John Sidney McCainKelly's lead widens to 10 points in Arizona Senate race: poll COVID response shows a way forward on private gun sale checks Trump pulls into must-win Arizona trailing in polls MORE (R-Ariz.) on Monday said President Trump “owes it to the American people” to explain his unfounded allegations that former President Barack Obama Barack Hussein ObamaGOP senator blocks Schumer resolution aimed at Biden probe as tensions run high D-Day for Trump: September 29 Obama says making a voting plan is part of 'how to quarantine successfully' MORE ordered surveillance of Trump Tower.

"The American people need to know what evidence he has to make such a charge — that’s a serious charge,” McCain said, as reported by NBC News.

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Trump over the weekend accused Obama of wiretapping Trump Tower before the presidential election.

An Obama spokesman denied that the former president or any White House official ordered surveillance.

"A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice," Kevin Lewis said in a statement.

"As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen," Lewis added. "Any suggestion otherwise is simply false."

The White House has called on Congress to incorporate an investigation into the alleged surveillance into its probe on Russia’s interference in the presidential election.

Rep. Devin Nunes (R-Calif.), who chairs the House Intelligence Committee, said on Sunday that his committee will investigate any potential surveillance of political parties as part of its Russia inquiry.

White House press secretary Sean Spicer did not provide reporters with additional evidence of Trump’s allegations during Monday’s press briefing.

“The question is: Is it surveillance? Is it a wiretap or whatever?” he asked. “But there’s been enough reporting that strongly suggests that something occurred.”