IN the 1988 presidential election the South will again be a key battleground. The ``Super Tuesday'' vote reminds us anew of the immense political changes there over the last quarter-century. The South has been the setting for the two most consequential electoral shifts in the United States since the New Deal: The ending of the restrictions that for so long kept blacks from voting and the realignment of black voters into Democratic ranks; and on the other side the movement of a large segment of the Southern white electorate further away from the national Democratic Party. The effects of both developments were evident March 8.
Jesse Jackson, who began his political career in the Southern civil rights protests, solidified his position on Super Tuesday as a figure in Democratic presidential politics. He did this by winning more than 90 percent of the black vote, which made up one-quarter of the entire Democratic primary vote March 8.
The size of the black vote in the South today and the near-unanimity with which it belongs to the Democrats present Southern Republicans with a major problem. In much of the region they must carry the white vote by nearly 2 to 1 if they are to win statewide elections. This is not easy to do, as the 1986 US Senate races attested. In Alabama, Georgia, Louisiana, and North Carolina, Democratic candidates swept to victory in November 1986 on the basis of overwhelming majorities among blacks, with only minority support among whites.
In presidential elections, however, the Democrats' base among whites has been so strikingly eroded that they find it hard to win even with a large margin from the black community. Surveys taken by CBS News and the New York Times on Super Tuesday found only 44 percent of those voting in the Democratic primaries saying they would definitely vote Democratic in November - 20 points lower than the proportion of Republican primary voters saying they would definitely back the GOP nominee.
The danger confronting the Democrats is not the possibility of the defection of the Rev. Mr. Jackson's backers. Amid near-unanimous speculation that the Democrats would not in fact nominate Jackson for president, 65 percent of those who had voted for him March 8 said they would definitely vote Democratic in November, while another 17 percent would probably back the party nominee.