Here is who attended a meeting at NRSC headquarters (10 Jun) to raise money for Thad Cochran. I have them listed below as well as any quotes they made on the issue
Source
Roger Wicker (R-MS) – Nothing from this meeting, but here is a different report on the issue.
Lisa Murkowski (R-AK) – Refused to explain why she was financially supporting Cochran. Contact her here or here and ask #whyThad
Rob Portman (R-OH) – “I am [supporting Cochran]. I’m the vice chair of the NRSC. We are supporting all our incumbents, including Sen. Cochran.”
When asked if he agrees with Cochran’s claim that McDaniel is an “extremist” who would be “dangerous” if elected, Portman demurred. “I didn’t see what he said, so I don’t want to comment on it,” Portman said. “But Thad’s a friend and he’s a colleague and he’s a good conservative and he’s been great for Mississippi.”
Lamar Alexander (R-TN) – “Because he’s one of the finest senators we have in the United States Senate.”
Orrin Hatch (R-UT) – No comment available for this but has commented in other forums.
Chuck Grassley (R-IA) – No comment available. Contact him here or here and ask #whyThad.
John Barrasso (R-WY) – “because he’s an outstanding conservative senator and voice for the people of his home state.”
John Thune (R-SD) – No comment available. Contact him here or here and ask #whyThad.
John Cornyn (R-TX) – Drew Brandewie from Senator John Cornyn’s office furnished a quote from the Senator for this story: “Senator Cochran has been a tireless advocate for the people of Mississippi who has voted to oppose, defund, or repeal Obamacare over 100 times.”
Bob Corker (R-TN) – No comment available. Contact him here or here and ask #whyThad.
Susan Collins (R-ME) – No comment available. Contact her here or here and ask #whyThad.
Kelly Ayotte (R-NH) – “Here to support Thad!”
Dean Heller (R-NV) – No comment available. Contact him here or here and ask #whyThad.
Richard Shelby (R-AL) – No comment available. Contact him here or here and ask #whyThad.