You probably won’t have massive voter fraud in any one state, just enough to make a difference in a close state.
In 1960, Texas and Illinois had highly suspicious results and probable cause to believe that there was massive voter fraud. But Nixon refused to demand a recount.
In 2000, there was a lot of voter fraud in Florida, but not quite enough to counteract the POd Cuban voters going overwhelmingly for Bush.
An acquaintance originally from the Chicago area, told me about coming home from college for Xmas that year. Ran into an old HS buddy (19 years old) who told him he had voted 18 times in the November election. Apparently he was paid so much per vote ... said it was easy money. Multiply that by several hundred people doing the same thing and you understand why there were voter irregularities in the Chicago area.
Nixon wanted a recount, but Dwight Eisenhower called him on the carpet and told him to shut up, the country couldn't take the scandal.
Joker in the deck: Ike never liked Nixon and didn't want him in the White House under any circumstances, so his argument was specious at best.
So Nixon knuckled under, and one stolen election, one Johnson dictatorship, and two dead Kennedys and a dead MLK later, a (justifiably) more paranoid Nixon was sworn in anyway.
Conclusion: Nixon should have stood up for himself and fought it out anyway. He was a square shooter in '60, less so in 1969, by which time he was more cynical and surrounded by cynical admen (J. Walter Thompson execs Haldeman and Ehrlichmann, self-promoting pompous hump Henry Kissinger).