Here's a road map for New Hampshire primary ballot race

''We are all marines now,'' says Paul Shone, state director of John Glenn's embattled presidential campaign in New Hampshire. Senator Glenn, a former marine, and his political warriors are dug in here for what on Tuesday could be the decisive Democratic struggle of Election '84.

The Mondale blitz in Iowa this week turned Glenn's political flanks in New Hampshire, and disrupted his careful march toward the primary four days from now.

Private polls by the Glenn campaign showed him behind Walter Mondale 46 percent to 18 percent in New Hampshire two months ago. Mr. Shone says a new poll , run just before Iowa, showed the margin had narrowed to 35 to 27. But that poll, even if it was accurate, is meaningless after Iowa. It's a whole new race. And Glenn's troops are braced for the worst.

Tuesday's vote is expected to show several things: Is Mr. Mondale really as strong as he looks? Has Gary Hart emerged as the strongest alternative to Mondale? Can Glenn regain his momentum? And can the Rev. Jesse Jackson turn his charisma into votes?

The Mondale machine, which has been methodically put together in New Hampshire over the past year and a half, continues to purr along like a fine-tuned Mercedes. Iowa kept that machine on course, and political observers here will be surprised if the former vice-president's vote isn't nearly double that of his closest rival.

Only a last-minute gaffe of enormous proportions could change those predictions. And the Mondale team is known for its ability to avoid just such mistakes.

If Mondale glanced over his shoulder at his closest rivals, he would probably first see Senator Hart. His second-place finish in Iowa has energized his campaign.

Dan Calegari, Hart coordinator in Manchester, says the change since Iowa has been phenomenal. New volunteers are showing up. People are calling from all over the country to offer money. Three hundred students will be arriving this weekend from across New England to pass out literature door-to-door.

For months, Hart campaigned almost alone. He was broke. He got little news media attention. Members of his staff went without pay.

Now, scores of TV cameramen and journalists follow his every move. Insiders at a number of other campaigns now privately say they think he will finish second here on Tuesday. This is obviously due in large part to Iowa. But it also stems from Hart's excellent New Hampshire team, led by Jeanne Shaheen in Concord.

But what if he does well here? Because his campaign has been so short of funds, he has been unable to file full delegate slates in some of the primaries on ''Super Tuesday,'' March 13. So he could have trouble following through. That could leave Mondale the only complete candidate on the playing field.

The man everyone had expected to place second here was Senator Glenn. Now the election is in such flux that his position seems very uncertain.

Alan Cranston's workers here say they have detected a sharp drop in Glenn support. Their phone canvasses were indicating last week that Glenn would get about 16 percent of the vote. Within two days after Iowa, that fell to only 8 percent. A canvass, of course, is not as accurate as a poll. But it can be a useful indicator.

Even so, the Glenn team is not sitting idle. It has put together a new five-minute TV ad that shows the candidate looking eyeball-to-eyeball at New Hampshire voters and stating his case in clear, unemotional terms. Supplementing that, 60,000 handwritten letters (done by volunteers) will go to independents Monday.

And this weekend, 400 volunteers from Ohio arrive. They will pass out 135,000 pieces of literature in Concord alone.

Then there's the Jackson phenomenon. Crowds love him. The words come slowly, quietly at first, then build to a crescendo that brings ovations. But does all this equal votes? Jesse Jackson was a minor player in Iowa. He campaigned there only one day. This time he is devoting a lot more time. He's opened six campaign offices. He's getting good media play.

But he has little money. A Jackson worker calls it ''a $30,000 campaign,'' which would be less than 10 percent of what the major players are spending. Yet he has been running third in some polls. Insiders consider Jackson a wild card, whose effect is hard to judge.

Briefly, here's a look at the four other major candidates vying here:

Alan Cranston. Disappointed by his fourth-place finish in Iowa, the senator nevertheless continues to fight hard in New Hampshire. Crowds are large and enthusiastic. One supporter here says he can still ''make a decent showing.''

Reubin Askew. No one has spent more time in New Hampshire (78 days) than the former Florida governor. He has a solid team, and is working hard to win Roman Catholic and conservative votes. That strategy didn't work very well in Iowa, but he has higher hopes here.

Ernest Hollings. The South Carolina senator has been waiting for Glenn to stumble so he could become the leading ''moderate'' candidate. Glenn's fifth-place finish in Iowa has already brought some Glenn supporters over to Mr. Hollings. His organization here, however, is no match for most of the others.

George McGovern. There is affection in the Democratic Party for the former South Dakota senator. He has played the role of senior statesman, and in Iowa they liked it - putting him in third place. Iowa, however, is next door to South Dakota, and he was looked at like a favorite son. He doesn't have that advantage here.