No, the Los Angeles Chinese Massacre of 1871 was the largest ever mass lynching,
There was a (1880s?) lynching/riot in Louisiana of 'Blacks' that was bigger as well,
And of course the Tulsa race massacre was larger still, although once a lynching flattens a town over the course of two days and kills hundreds of people, I reckon it ain't a lynching no more,,,
That senator was not killed because he was a Republican, he was killed because of his activities organizing 'Blacks' as well as getting voted into office largely by them, his activities even getting him booted out of his own church.
Not political party affiliation, but racial activities affiliation.