"At such a time when it becomes necessary, the President also needs to speak directly to the Saudis and say enough's enough," Ernst said. "And if there are indicators coming from those intelligence agencies, he also needs to be involved in some sort of action."
One bipartisan proposal in the Senate calls to impose additional sanctions on Saudi Arabia and others thought to be fomenting unrest in Yemen and to stop the sale and transfer of all weapons to Saudi Arabia until the Yemen campaign is scaled back.
A bipartisan pair of senators also have invoked the Global Magnitsky Act, which enables sanctions over human rights offences, to force Trump to formally say within a few months whether he thinks Mohammed was responsible for Khashoggi's death.
Lee added that he hoped mounting fury at Saudi Arabia would become "an opportunity for the Congress to weigh in and say, let's halt our efforts in Yemen".
"Congress has to take some ownership of US foreign policy," he said.
Thus far, however, efforts in the House and the Senate to pass legislation that would use the War Powers Act to curtail US military and intelligence support for Saudi Arabia have either fallen short or been stymied by leaders before they could ever get to the floor.
That leaves lawmakers with the option of launching investigations - something Ernst, newly appointed to the Senate Republican leadership team, endorsed.
"I do think we need to look into this further, and we need to understand where the investigations are leading us," she said, adding that she hoped senators would receive more briefings from intelligence officials on Mohammed's role.
In the House, Democrats are promising to tackle the Khashoggi matter when they take over the majority next year - and are openly questioning whether Trump's defence of the crown prince is motivated by self-interest.
"Is his personal financial interest driving US policy in the Gulf, is it driving US policy vis-a-vis the Russians? We don't know, but it would be irresponsible not to find out," Congressman Adam Schiff, the ranking Democrat and expected new chairman of the House Intelligence Committee, said on State of the Union, accusing Trump of being "dishonest" about the Crown Prince's involvement.
"It telegraphs to despots around the world they can murder people with impunity and that this president will have their back as long as they praise him, as long as they do business with him potentially," Schiff added. "That cannot be the guiding principle behind our foreign policy."
Other Democrats questioned whether Trump simply had a soft spot for despots.
"Why does Trump have such an affinity for murderous autocrats? He defends Vladimir Putin of Russia, fell in love w/ Kim Jong Un of N Korea, admires Rodrigo Duterte of the Philippines & now refuses to accept CIA findings that the Saudi Crown Prince ordered #JamalKhashoggi's murder," Congresswoman Maxine Waters, the ranking Democrat and expected new chairwoman of the House Financial Services Committee, tweeted.
Both Waters and Schiff will be in a position to closely scrutinise Trump's finances in connection with Saudi Arabia and other foreign governments next year.
