Despite the victories Tuesday that refueled their lagging campaigns, Edward M. Kennedy and George Bush face even steeper paths to nomination today than confronted them after their twin drubbings in Illinois a week ago.

The mathematics of the presidential balloting in the Democratic and Republican parties requires Kennedy and Bush to win about five of every eight delegates remaining to be chosen if they are to overhaul front-runners Jimmy Carter and Ronald Reagan.

In Tuesday's voting in New York and Connecticut, neither challenger was able to meet that standard, so both fell further behind the pace they must maintain to make their longshot victory hopes come true in the Detroit and New York City conventions.

By upsetting Carter in both states, Kennedy won 193 of the 336 delegates at stake Tuesday -- 57 percent of the day's prize. That is impressive, but not enough to overhaul Carter's present lead if the same percentage is maintained in all remaining primaries and caucuses.

For Bush, the performance fell much further short of the standard he must achieve to catch Reagan. Bush won Connecticut, but so narrowly that he gained only 15 delegates, to Reagan's 14, and 6 for Rep. John B. Anderson. In the New York delegate contest, it was Reagan 91, Bush 6, Anderson 1 and uncommitted 19.

Overall, Bush won only 21 of the 152 delegates, a 14 percent margin that, if maintained, would soon find Reagan moving almost entirely out of Bush's striking range.

As the accompanying table shows, early-season victories have given Carter almost exactly half of the delegates he needs for nomination, and Reagan almost one-third of his magic number.

Most, but not all, of those delegates are legally bound to vote for the candidates they are supporting, and the chances of dislodging any of them are probably not great unless Bush and Kennedy start winning by bigger margins and with more consistency than they have shown so far.

Still, neither challenger is conceding a thing. Nor, for that matter, is Anderson, who has yet to win his first primary.

David Keene, political director of the Bush campaign, said the former ambassador's nomination is "improbable but not impossible." For Bush to have a chance, Keene said, he would have to defeat Reagan soundly in Pennsylvania, Maryland, Michigan, Oregon, New Jersey and Ohio.

Even then, Reagan can close strongly by winning the 168 delegates in his home state of California where in its winner-take-all primary on June 3, he is currently a strong favorite and by taking most of the 133 delegates in five western convention states -- Arizona, Colorado, Oklahoma, Utah and Wyoming -- where he enjoyed a near-sweep in 1976.

Keene maintained, however, that if Bush beat Reagan in such key states as Pennsylvania, Ohio and New Jersey, some of the present commitments to Reagan would shake loose. Many of the delegates in Llinois and New York, now counted in the Reagan column, are not legally bound to him, Keene said.

A similar strategic concept underlies Kennedy's hopes for unseating Carter. Richard Stearns, the architect of the Kennedy victory in Connecticut and the senator's chief delegate-hunter, said it would take a combination of impressive Kennedy victories and political nervousness about Carter's November prospects to give the challenger a crack at the incumbent.

Kennedy and Bush are both essentially running for strong second-place finishes in next Tuesday's primaries in Wisconsin and Kansas, while aiming for victory over the front-running Carter and Reagan in the April 22 Pennsylvania contest.

Kennedy's path then points to Michigan en route to the June 3 grand-slam in New Jersey, Ohio and California. In the Democratic Party, however, California is a proportional-representation primary -- not winner-take-all -- and Kennedy is given a better chance of beating Carter than Bush is of upsetting Reagan for control of the single largest delegation.

But Carter, like Reagan, has strength of his own to tap to the closing stages of the contest. There are primaries yet to come in such southern and border states as Louisiana, Tennessee, North Carolina, Arkansas and Kentucky, where the president will be a strong favorite. And Carter has employed his organizational advantage over Kennedy to great effect in the caucus states. Many of these are still to come.

While Stearns said a Kennedy victory is "certainly within the realm of possibility," another senior member of the Kennedy staff was probably being realistic when he said, "New York and Connecticut mean that Carter can't lock this up before June 3. And two months -- or even two weeks -- can be a lifetime in the kind of political climate we've seen this year."

But in the real world of the political accountants, where delegates, not headlines, are the currency, Carter and Reagan are still on track to nomination.