I am sure they have tried to blame Republicans for it
John Kenneth Gailbraith actually made a similar accusation at the time.
It’s in Manchester’s book.
The Death of a President: November 20-November 25, 1963 by William Manchester
Harvard economist John Kenneth Galbraith was a liberal (actually, socialist) member of the Kennedy administration. On the afternoon of the assassination, before he knew that Oswald had been arrested, he told Arthur Schlesinger:
“We let the Right inject this poison in the American bloodstream and this is the result.” (William Manchester, Death of a President, p. 354)
Galbraith remarked to Schlesinger, We let the Radical Right
inject this poison into the American bloodstream and this is the result.
Almost all of the White House family assumed that the assassination had been the work of the Radical Right.
Later that day, Schlesinger echoed the thought, You know,
the Radical Right has never been taken seriously in this
country.
http://www.davekopel.org/schlesinger/Schlesinger-chapter-9.pdf