The Dems ‘owned’ the senior vote until recently. The elderly who spent decades voting for FDR by any other name have now passed on. The “Republicans will take your Social Security” ruse Dems pulled out in every election just won’t work any more.
I wouldn’t say this generation of seniors are in the Republican camp so much as that they are open to voting for either party. The GOP shouldn’t take them for granted now as a constituent group, as the Dems did.
I just took a look at presidential elections back to 1968 and it doesn't look that way to me, do you have some figures to support that? They usually vote Republican except for 1992,1996, and 2000.