What would've happened if Barry Goldwater voted for the Civil Rights Act and tried to unite the GOP?

[Blow by blow, the passion dies]

I can see a Southern segregationist third-party campaign, and Goldwater sweeping the West.

[Agonized-Statism]

Goldwater wins the traditional Republican strongholds while still losing badly. The popular idea is that George Wallace runs, but his plan since 1963 was to challenge the incumbent in the primaries, not run a third-party campaign. Ross Barnett is a more likely standard bearer for a 1964 Southern segregationist party.

[One Term Floridian]

I can honestly see Goldwater doing even worse in the Electoral College here, albeit with the reward of him doing a bit better in the blue states. LBJ was extremely popular at this time and this scenario has Goldwater giving away his one major base in the country: the South. Goldwater splits enough votes with a southern racist and narrowly gives GA to LBJ.

[Fuzzy Bear]

If Goldwater had voted for the Civil Rights Act of 1964 he would have appeared far more reasonable.  Rockefeller, Romney, Javits, et Al, would have given their endorsement, instead of remaining neutral.  He may have carried TN and VA.  He likely would have carried NE, OK, KS, WY, UT, ND, and SD.

What would NOT have happened in such an event was the path to victory in the GOP that the Goldwaterites were to enjoy.  Such a move would have stopped the development of the Southern wing of the GOP.  The Republican Party would not have become the conservative party it is now at the rate it did.

[Mr. Smith]

Goldwater flips the Upper South, and hold Utah, Idaho, and Vermont. A segregationist takes the Deep South.

LBJ eats the rest.