GOP senator: 'Not appropriate' to ask foreign governments to investigate Biden

“The president should not have raised the Biden issue on that call, period. It’s not appropriate for a president to engage a foreign government in an investigation of a political opponent,” Portman told The Columbus Dispatch
Portman is the latest GOP senator to distance themselves from Trump's public overtures to have Ukraine and China investigate Biden and his son, Hunter Biden. 

Speaking to reporters outside the White House on Thursday, Trump suggested that China and Ukraine should investigate the Bidens.  

The president added that he had not explicitly asked Chinese President Xi Jinping to open such a probe but that it’s “certainly something we can start thinking about.”
House Democrats are at the start of an impeachment inquiry centered on Trump asking the Ukrainian government to work with his personal lawyer, Rudy Giulani, to look into the Bidens, and allegations that he tried to withhold aid to Ukraine in an effort to get Kiev to launch such a probe.
Collins, over the weekend, called Trump's remarks "completely inappropriate" and said she thought he made a "big mistake by asking China to get involved in investigating a political opponent."

Sasse said in a statement on Thursday night that "Americans don’t look to Chinese commies for the truth."  And Romney pushed back forcefully, calling Trump's rhetoric "wrong and appalling."

No Senate Republican has backed the House's impeachment inquiry. 

“I don’t view it as an impeachable offense. I think the House, frankly, rushed to impeachment assuming certain things," Portman added to the Dispatch.