I suggest that you change the title of the thread here to make it more specific. There are any number of ways Jimmy Carter might not have been elected president in 1976. Gerald Ford might have defeated him, Carter might have lost the primary to Mo Udall, etc. You are interested in only one of the possible ways of stopping Carter--namely have Reagan win the GOP nomination and then the general election. The title of the thread should reflect that. E.g., "Reagan elected in 1976."
As to a possibe Reagan victory in 1976: [1]
One thing to remember: If Reagan is elected at all, it will probably be very narrowly. (The GOP will be much more divided than in 1980--after all, it will just have narrowly repudiated its incumbent president!-- eight years of Republicans in the White House are bound to produce some swing to the Democrats, Watergate will hurt the GOP to some extent under any nominee, Jimmy Carter in 1976 will not have the record to defend that he did in 1980, etc.) Thus, the Congress elected in 1976 will probably look far more like the one elected in OTL's 1976 than that with which Reagan would deal after OTL's 1980 (where Republicans took control of the Senate and with conservative Democrats gained something like de facto control of the House). I don't say that Reagan's 95th Congress will be 61-37 D in the Senate and 291-144 D in the House
https://en.wikipedia.org/wiki/95th_United_States_Congress but if--as I think--Reagan will do only marginally better than Ford (but just enough to win OH and MS and therefore the election) it will be pretty close to that. And if the usual pattern of the party controlling the White House losing seats in a midterm holds, the 96th Congress will be still less favorable to Reagan.
The result is that whether you think 1980s Reaganomics in terms of tax cuts, deregulation, etc. was a good or bad thing, we are not likely to see much of it in 1977-81--at least in so far as it depends on legislation. (Admittedly Reagan could do some deregulatory things by executive action--indeed, Carter did some of that...)
[1] On balance I think it likely that Reagan if nominated will lose narrowly in Novemver for reasons I go into at
https://www.alternatehistory.com/forum/threads/wi-reagan-vs-carter-1976.468970/#post-19035525 but I can't rule a narrow Reagan victory out.