Had Wallace not been shot, he likely would have won a greater percentage of the popular vote in 1972 than he did in 1968, when he received about 13%. You must remember that in 1972, conservative dissatisfaction with Nixon was as high as it is against the present incumbent, who of course is a lame duck. Nixon strayed further from conservative orthodoxy than George W. Bush has, and with Wallace offering a populist, social conservative alternative to the antiwar liberal McGovern, there would have been substantial defection to the Alabama governor. Add in white Southerners and white union members in the Rust Belt and the Eastern Seaboard, and it is quite likely that Wallace would have gotten at least 20% of the national vote, slightly better than Ross Perot's 1992 showing. Wallace may well have won states beyond the Deep South, like Texas, Oklahoma, Tennessee, and North Carolina. The rest of the map would have been hard to predict. Conservative defections to Wallace might have put solidly Republican states like Kansas and Indiana in play. Large defections to Wallace among blue collar Democrats could well have had a reverse effect in normally Democrat-leaning New York, Michigan, and Pennsylvania.
Had Wallace achieved a deadlock in the Electoral College, he could have well struck a deal not unlike that of 1876, where Democrat supporters of Samuel Tilden in the South switched their vote to the Republican Rutherford Hayes in exchange for the withdrawal of Federal troops from the South, thus ending Reconstruction and re-establishing white majority rule in the secessionist states. Had Wallace insisted on court packing to increase the Supreme Court to 15 justices, with the six appointees to be strict constructionists, Roe v. Wade (already decided during the 1972 election, and the opinion issued in January 1973) would have been overturned, and school busing for integration would have ended. Other liberal Warren Court decisions, like "one man, one vote", Miranda, and banning of public school prayer, would have been overturned.
Any such possibility ended in a shopping center in Maryland because of the act of a demented man, Arthur Bremer.