What was the significance of a number of conservative democrats changing their party affiliation beginning in 1964?

Democrats had been losing elections in what had long been considered solid Democratic territory in the South. Lyndon B. Johnson, a Democrat who took up the presidency after John F. Kennedy was assassinated, had become associated in the minds of voters with the civil rights movement. The civil rights movement aimed to give black Americans equality. This did not sit well with white voters in the South. In the 1964 presidential election, the Republican candidate, Barry Goldwater, won the states of Louisiana, Mississippi, Alabama, Georgia, and South Carolina. Nevertheless, Johnson prevailed and won the election. But it showed conservative Democrats were willing to shift to the Republican party if they felt it more closely aligned with their views.