The celebrated North Carolina race--which some say will overshadow the Presidential race in rhetoric if not reality--pits the scourge of right wing conservatism, Sen. Jesse Helms, against Democratic Gov. James B. Hunt, Jr. Polls taken late last year put the popular Hunt-progressive in Southern terms--ahead of Helms by as much as 20 points, though more recent polls show that Helms has closed the gap.

In what promises to be one of the most expensive races in the country, Democrats hope to counter superior Republican fundraising ability with a flood of Black voter registration, which is likely to aid Democratic candidates throughout the South.

In Iowa, Republican incumbent Roger W. Jepsen, has also closed a polling gap on his Democratic challenger Rep. Tom Harkin. But Iowa seems to have a distaste for incumbents--no senator has won a second term there since 1966 Senate Majority leader Howard Baker's decision to step down in Tennessee induced the popular Democrat Rep. Albert Gore Jr. to make a bid for the seat. Gore will probably benefit from a fractious Reublican primary, in which an extreme right-wing religious leader has been viciously attacking his moderate foe.

Texas, where Sen. John Tower is retiring, presents a different situation, because a difficult Democratic primary is expected before the winner faces likely Republican nominee Rep. Phil Gramm. Tower squeaked by with 50 percent in his 1978 election.

Democrats would particularly like to unseat prominent Sen. Charles H. Percy of Illinois, chairman of the Foreign Relations Committee. Although a moderate on social issues, Percy has stood quietly, but staunchly, behind President Reagan's economic program. He faces a strong challenge from the right, from the more uniformly conservative Rep. Tom Corcoran, in what will probably be the only GOP primary for an incumbent.

The most attractive Democratic candidate in Illinois would probably be Rep. Paul Simon, who is stepping down from the Congressional seat he has held for ten years. But Simon, whose vocal support for higher education funding as chairman of the House Subcommittee on Post-secondary Education has helped win him respect from liberals, must overcome three rivals in the Democratic primary.

Other vulnerable Republican Senators include Thad Cochran of Mississippi, who, like Helms and Jepsen, has trailed his Democratic challenger in polls, Gordon J. Humphrey of New Hampshire, and Rudy Boschwitz of Minnesota. Observers say Walter F. Mondale, also from Minnesota, could play a role in Boschwitz's fate, if he lands the Democratic presidential nomination. Mondale's ticket would rouse a strong Democratic turnout at the Minnesota polls in November.

Republicans, on the other hand, could mount particularly strong challenges in Rhode Island and West Virginia, but they have not yet been able to persuade their first-choice candidates to challenge the Democratic incumbents.

In Rhode Island, everyone, including GOP officials, has said that Rep. Claudine Schneider will not run for the seat held by four-term Sen. Claiborne Pell. Everyone except Schneider herself, that is, who says she is still pondering a shot at the Senate.

GOP attempts to draft former West Virginia Gov. Arch A. Moore Jr. in the race against present Gov. John D. Rockefeller IV have so far been unsuccessful. Moore could provide Rockefeller with a tough fight for the seat from which long-time Senator Jennings Randolph is retiring.

House races will surely be less tumultuous than the Senate because less is at stake. Republicans would have to make extraordinary gains to challenge the majority control Democrats have held in the House for 28 years. And in House races, where issues are generally less important than personality factors, nationwide trends tend to blur in significance. Still, insiders who talk about the races make a few basic points:

Republicans and Democrats agree that the 52 Democratic freshmen form the critical group in the House elections.

Voting trends show that the country is becoming more sympathetic to incumbents after a period of hostility spurred by Watergate. Republicans want to nip the Democratic freshmen in the bud before they gain the vaunted status of political old-timers.

Republican strategy, according to Republican Lotterer, is to cast the races as a "Reagan vs. Mondale-O'Neill" contest. Lotterer says that the Democratic freshmen have simply fallen in lockstep behind effective Democratic party leader Rep. Thomas P. O'Neill Jr. (D-Mass.), whose old-fashioned liberalism he thinks is out of favor with much of the electorate.

But Johnson of the Democratic Congressional Campaign Committee argues that "our people aren't ideological like the 52 Republican freshmen who won in 1980."