By Susan Cornwell, Doina Chiacu and Daphne Psaledakis
WASHINGTON, Jan 10 (Reuters) - A second Republican U.S. senator called on Sunday for President Donald Trump to resign, saying he could face criminal liability after the deadly storming of the U.S. Capitol by his supporters.
The remarks by Senator Pat Toomey, a conservative supporter of Trump until recently, came as Democrats in the House of Representatives prepared to move forward with impeachment proceedings and amid federal investigations of Wednesday's assault on the seat of government.
The Justice Department charged two more people in connection with the attack on the building, and one lawmaker said the U.S. army secretary had told lawmakers at least 25 terrorism cases had been opened as a result of the assault.
Republican Trump, who has challenged the validity of President-elect Joe Biden's Nov. 3 election victory, praised and egged on his supporters before they laid siege to the Capitol, where lawmakers were certifying the Electoral College vote for Biden.
"I think the best way for our country is for the president to resign and go away as soon as possible," Toomey told NBC.
A top Democrat suggested lawmakers might wait to send the impeachment article to the Senate for a trial to give Congress time to approve Biden's Cabinet nominees and other agenda items. Democrat Biden takes office on Jan. 20.
"Let's give President-elect Biden the 100 days he needs to get his agenda off and running," House Majority Whip James Clyburn said on CNN.
Toomey said he did not think impeachment was viable with only 10 days left in Trump's term, and noted there did not appear to be a consensus to use the Constitution's 25th Amendment to strip Trump of his powers.
He told CNN he believed Trump could be held criminally liable in the events at the Capitol.
Lisa Murkowski on Friday became the first Republican U.S. senator to say Trump should resign immediately. Republican Ben Sasse said he would "definitely consider" impeachment.
It was unclear whether a significant number of other Republicans would follow suit. Republican leaders have urged the Democratic-led House not to initiate impeachment proceedings for a historic second time against Trump.
An adviser said Vice President Mike Pence opposed using the 25th Amendment to remove Trump.
Senator Roy Blunt, a member of the Republican leadership, said on CBS he did not think Trump should resign but that he should be "very careful over the next 10 days."
The White House said Trump planned to leave Washington to visit Texas on Tuesday.
House Speaker Nancy Pelosi has made it clear impeachment was not Democrats' first choice, but she embraced the move if Trump is not removed by other means.
Democratic Representative Ted Lieu said there were now 200 co-sponsors for the impeachment legislation he will introduce on Monday. The House could take up impeachment on Tuesday or Wednesday, Clyburn told CNN.
Biden has said he will leave the impeachment question to Congress. He did say Congress must be able to hit the ground running once he takes office, when he will focus on the coronavirus pandemic and economic recovery.
Five people including a Capitol Police officer died as a result of Wednesday's rioting and dozens of people have been charged following the storming of the Capitol.
Authorities are investigating the security lapse, with some lawmakers questioning whether rioters had help from inside the building after images emerged of some police officers opening barricades and posing for selfies with the rioters.
The ripple effects persisted on Sunday. The attending physician for Congress warned lawmakers in a letter they may have been exposed to COVID-19 while in lockdown during the riot.
Hundreds of officers lined a street near the Capitol to honor the slain officer, Brian Sicknick, as his remains were driven by. The White House lowered its flags to half staff on Sunday, two days after flags at the Capitol were lowered in his honor.
If found guilty after leaving office, Trump would lose benefits enjoyed by former presidents, such as security and pension, and the Senate could vote to bar him from running for another term.
(Reporting by Susan Cornwell, Doina Chiacu, Linda So, Daphne Psadelakis, Steve Holland, Nandita Bose, Andrea Shalal, David Shepardson; Writing by Doina Chiacu and Patricia Zengerle; Editing by Bill Berkrot and Peter Cooney)
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