Vice President Bush holds a commanding lead in virtually all the 16 states holding primaries on March 8, "Super Tuesday," while Massachusetts Gov. Michael S. Dukakis and Jesse L. Jackson are neck and neck for the lead on the Democratic side.

The Washington Post-ABC News Poll found that Bush holds nearly a 3-to-1 lead over his closest competitor, Sen. Robert J. Dole (Kan.), among likely voters in these Republican primaries. In the Democratic contest, half the likely electorate is split evenly between Dukakis and Jackson, while Sen. Albert Gore Jr. (Tenn.) follows with just under 20 percent and Rep. Richard A. Gephardt (Mo.) trails the front-runners with just under 15 percent.

In addition to gauging the head-to-head competition, the poll offered insights into the Democratic and Republican electorates before the largest collective primary in the nation's history. Among the findings:Pat Robertson's Christian insurgency has failed to materialize so far as a serious challenge to Bush in any state -- unless Robertson's supporters have been undercounted, as they have in other surveys. While running third overall, far behind Bush and well behind Dole, the former television evangelist is in a position to take second place away from Dole in Oklahoma and Alabama. Dukakis, who has been identified with the reform- liberal wing of the Democratic Party, is fully competitive among Democrats who identify themselves as conservative. With those Democrats who place themselves on the right of the ideological spectrum, Dukakis and Gore are both leading, each getting about one-quarter of this wing. Dukakis holds a modest advantage over Jackson among Democrats who say they are liberal, and he leads among moderates. When Bush ran for the presidency in 1980, he was generally viewed as the moderate in the GOP race, challenging the more conservative Ronald Reagan. This year, Bush is stronger among conservatives, who back him over Dole by almost a 3-to-1 ratio, than among moderates, who support Bush over Dole by considerably less than a 2-to-1 ratio. This finding suggests that Bush has succeeded, at least for the present, is placing himself under Reagan's conservative umbrella. Robertson's voters continue to be drawn from the most religious segment of the Republican electorate. The survey showed that eight of 10 Robertson voters described themselves as "born-again," and seven of 10 considered themselves evangelicals or charismatics.

Southern born-again Christians and evangelicals are, however, far from united behind Robertson. Bush wins the plurality of the born-again and evangelical vote. Robertson is burdened by high negative ratings: 44 percent of likely Republican voters said they definitely would not vote for Robertson, up from 32 percent in an ABC poll completed before the Iowa caucuses. Less than 10 percent of all likely Republican voters have similarly low opinions of Bush or Dole.

The increase in Robertson's negative ratings may be attributable to recent highly publicized remarks, including unsubstantiated claims that his staff at Christian Broadcasting Network knew the whereabouts of hostages in Lebanon, that Bush's campaign may have leaked damaging information about the Rev. Jimmy Swaggart and that offensive nuclear missiles are now maintained by Cuba.

Dole, according to the poll, faces an uphill fight attempting to oust Bush from the front-runner spot. Just under 60 percent of the 946 likely Republican voters surveyed said Bush is their first choice; Dole had the support of just over 20 percent and Robertson was slightly over 10 percent. Rep. Jack Kemp (R-N.Y.) remains far behind with 5 percent.

At the time the survey was taken, Feb. 17-28, Dole was running even with Bush only in Missouri and Maryland. In Arkansas and Rhode Island, the next closest states, Bush appeared to hold a margin of slightly better than 10 percentage points. In the 12 other Super Tuesday states, Bush held the allegiance of large majorities.

On the Democratic side, the contest is much closer, and more susceptible to change in the six days of an increasingly harsh campaign in which Dukakis appeared to be gaining strength, according to the survey of 1,121 likely Democratic voters.

Support for Dukakis has been surging since the start of the primary and caucus season, almost tripling since an earlier survey completed on Feb. 6. Similarly, Gephardt, who won in Iowa and South Dakota, has seen his level of support nearly double. Gore, in contrast, has seen only a slight gain, while the percentage of voters backing Jackson has fallen modestly.

Delegates to the Democratic and Republican conventions are won on the basis of state-wide votes and votes in congressional districts (or in the case of Texas, state senate districts). The Post-ABC poll does not provide detail at the district level but, with varying margins of error, it does provide a rough guideline pointing to the leaders in each of the 16 states.

On that basis, Jackson has the edge in four states -- Mississippi, Georgia, Alabama and North Carolina -- and he is roughly tied with Dukakis in Arkansas, Florida, Texas and Virginia, while Louisiana voters appeared to be split among Jackson, Dukakis and Gore. Dukakis holds a strong lead in three states -- Massachusetts, Rhode Island and Maryland. Gore leads in two states, Tennessee and Kentucky, while Gephardt is ahead in Missouri. Oklahoma appears to be a three-way contest among Gephardt, Gore and Dukakis.

More recent surveys of Texas and Florida with larger samples, released by Gallup-WJLA last night, show Dukakis holding a strong edge in both states -- leading in Florida by 15 percentage points. In addition, the Gallup-WJLA polls show significantly less support for Jackson in Florida, and more support in both states for Gephardt than shown in the Post-ABC poll. These two megastates are delegate gold mines, choosing 319, or one-quarter, of the 1,307 Democratic delegates to be elected March 8.

In addition, a Feb. 12-17 survey of North Carolina voters published by the Raleigh News and Observer found much less support for Jackson than the Post-ABC poll. The News and Observer poll found that Gore held a slight lead, followed closely by Jackson, Gephardt and Dukakis.

The Post-ABC survey indicates that Gore and Gephardt are battling for a similar segment of the electorate. For each of them, the proportion of supporters who identify themselves as conservatives is nearly double the number who say they are liberal, in contrast to Dukakis and Jackson, who get more liberal than conservative support. In addition, the largely white base of Gore and Gephardt support is less well educated than the largely white base of Dukakis support, and these Gore and Gephardt voters are older than either Dukakis' or Jackson's.

In sharp contrast to his competitors, Gore, who has attempted to stake out a conservative position on defense issues, receives significantly more support from men than women, the mirror opposite of Dukakis and Jackson. Gephardt's support is split evenly between sexes.

The struggle between Gore and Gephardt is reflected on the campaign trail, where Gore has a new set of television commercials that criticize Gephardt without naming him and make a direct appeal to the blue-collar manufacturing workers among whom Gephardt has shown strength.

The struggle between Gore and Gephardt is critical for both, because Democrats allocate delegates on a proportional basis, with a 15 percent cutoff. Gore is hovering within 5 points of 15 percent in seven states, and Gephardt in nine states. In any state where a candidate fails to get 15 percent, he will not qualify for any of the state-wide delegates.

In contrast to the Democrats, Republicans allocate delegates on the basis of winner-take-all for the candidate getting a plurality at the district or state-wide level in most states. This system should provide Bush with a major advantage because he can currently afford to absorb considerable erosion of support while retaining enough votes to win a plurality.

Staff polling analyst Kenneth E. John contributed to this report.