There is still time for political pratfalls before Northern Virginians begin electing delegates this month to state and national presidential conventions.

But local Democratic and Republican pundits say unless Jimmy Carter and Ronald Reagan suffer unforseen setbacks in Virginia, they will easily win the major share of their party's convention vote.

Virginia will have 64 delegate votes at the Democratic National Convention in New York City this August, and 51 votes at the Republican National Convention in Detroit this July.

Carter supporters, while publicly expressing respect for Sen. Edward Kennedy's strength, are privately predicting that the president will win at least 80 percent of Northern Virginia's 601 delegate votes at mass meetings on March 22. California Gov. Jerry Brown is not expected to win a single delegate.

Reagan will have a tougher contest with Republican candidate George Bush. But Virginia is Reagan country, say his supporters. That was proved four years ago when he overwhelmed President Gerald R. Ford in the state delegate contest. After Reagan's impressive victory last month in New Hampshire, he will be expected to win no less than 50 percent of the 650 delegate votes up for grabs during local Republican contests in the next two months. $"The way the caucus system works anything can happen if enough people get organized to do it," says Emilie Miller, past chairman of the Fairfax County Democratic Party, who remembers the caucus blitz of 1972 by supporters of George McGovern. "But there doesn't seem to be the mood for that right now."

Because Virginia voters do not register by party, the state is prohibited by both parties' national committees from holding direct primaries. Instead, delegates to state and national conventions are chosen by a lengthy and complicated system of local mass meetings and congressional district conventions.

Supporters of the state caucus system claim that it promotes more dedicated involvement at the local level. Opponents say the system helps keep party regulars in firm control. For those regulars, the caucus system provides a quadrennial opportunity to serve as elected delegates at state and national conventions.

"Getting elected (as a delegate) is just being a practical politician," says Miller, who adds it is crucial for maintaining power in the local party. Besides, she says, it is only fair that the people who work for the Democratic party during the three off years get rewarded with delegate duties during the presidential year.

Miller, who will be running as a Carter-Mondale delegate, knows the benefits that accompany a high political profile: "During the last year I've been to the White House so many times, somebody suggested they put a cot in there for me."

The Democratic mass meetings in Northern Virginia's 8th and 10th Congressional Districts will be March 22 at 18 public halls and high school auditoriums, the same day as all other Democratic meetings in Virginia.

Each of Northern Virginia's Republican parties will hold separate delegate selection meetings, beginning with the Alexandria GOP party canvas on Tuesday and ending with the Arlington GOP mass meeting May 10.

The Democratic and Republican delegate selection processes differ and, not surprisingly, each claims the other's is less representative.

The Democratic mass meeting resembles a schoolyard full of kids choosing sides for a game of tag. Participants align themselves by presidential preference or in uncommitted groups. For a group to win representation, it must have at least 20 percent of the total caucus. For instance, if 100 persons attend the mass meetings at Kenmore Intermediate School in Arlington and only 19 congregate for Brown, that group must disband and join another group that has at least 20 people or leave the room.

"We felt 20 percent was a reasonable number," says W. Raymond Colley, the Democratic chairman for the 8th Congressional District who proposed to the State Democratic Committee that the 15 percent minimum of four years ago be raised. "We felt if you didn't have at least 20 percent, you're not viable."

Nick Panuzio, chairman of the Fairfax County Republican Party says the Democrat's 20 percent minimum restricts votes. "There's a myth about the Democrats being an open party . . . The process of the Democratic party is a lot more closed than ours."

In some areas, such as Fairfax County, the Republican selection process involves one step more than the Democrats'. Republican delegates who are elected at local meetings must be reelected at a county meeting before they are eligible for the District convention. Democrats argue that the two-step process is intentionally designed so that only party regulars will persevere.

"It would take a genius to figure out their process," says Miller. "It's bad enough getting people out to one meeting, but two is very confusing."

The GOP delegate selection process in Alexandria differs from the rest of the state.It most resembles a mini-primary, with voters going to four polling places in the city to elect 285 delegates who will be allowed to cast one-fifth of a vote each at the District convention.

Nancy McCabe, chairman of Alexandria's Republican Party, says 174 persons have filed as delegate candidates on a Ronald Reagan slate. A total of 214 other delegate candidates are either split among the five remaining Republican hopefuls -- Baker, Anderson, Bush, Dole or Crane -- or are running uncommitted.

"Reagan definitely appears to have more solid support than any individual candidate," says McCabe, who is seeking election as an uncommitted delegate.

Four years ago, Northern Virginia Democrats elected twice as many uncommitted delegates to the state convention as Carter delegates. But with Carter in the White House and increasing world tensions, Democratic party leaders say his support ths year should be solid.

"It's an uphill fight," admits Barbara Phillips, chairman of the Democrats for Kennedy in the 10th District. "A lot of people say they will come (to the mass meetings), but exactly what will happen March 22 I don't know."

Arlington Democrat James Shelton is leading a move for an uncommitted slate of delegates to the national convention in New York City this August. sHe admits that getting the necessary representation at Arlington's mass meeting will not be automatic.

"We've got a hard scrap to get 20 percent and I realize it," says Shelton, a retired college professor and IRS attorney who argues that the "turbulent" events on the domestic and international scene demand an uncommitted group of Democrats. "What would happen if some of the hostages were killed over there?"