Each morning at 6 in Denver, Matt Wanning puts on his earphones, hauls out his Rolodex and his East Coast telephone books and settles in for a day of following the sun west.

By the time it is an orange ball low over the Rockies, Wanning has labored his way across the continent, touching down, by telephone, in Los Angeles.

He has already made perhaps 100 calls, many of them to strangers: lawyers, businessmen, political activists. His voice is raspy, "but it doesn't matter," he says. "Everyone in L.A. has an answering machine anyway."

Wanning is national finance director for Sen. Gary Hart (D-Colo.), and his is the good, gray, crucial grunt work of presidential fund-raising in The Year Before.

Bigger campaign staffs have more people doing what Wanning does, but no one has figured out a way of doing it differently or with more glamor.

It is also the least pleasant but most necessary part of the early campaign. The candidates treat it accordingly.

Sen. Alan Cranston (D-Calif.) is an exception: a politician who goes after the greenbacks with almost legendary relish.

"Other politicians can't ask for money," he says, "I can and do."

Cranston personally makes as many as 50 fund-raising calls a day.

"Whenever he has a free moment, he's always asking one of us, 'Where are my phone lists?' " says Sarah Muyskens, Cranston's finance director. "And once he gets on the phone, he really knows how to nail people."

More typical is former vice president Walter F. Mondale, who prefers to let others do the fishing. Of his campaign staff of 75, about 35 spend full time on fund-raising.

Between now and the 1984 national conventions, all six Democratic candidates will be shooting for a jackpot of about $24 million apiece, the maximum they can raise in the primary season under the federal campaign finance laws. If they plan well, roughly a third of that will be federal funds matching individual contributions of $250 or less.

The three easiest ways to finance a campaign are through big money, momentum money and PAC (political action committee) money. For presidential candidates, these sources are restricted, however, by the law, the calendar and the dictates of custom and strategy.

Big money was outlawed in campaigns for federal office a decade ago by the federal campaign finance reform laws.

"Momentum money" is governed by the calendar, its potential value dramatically dictated by the timing of the primaries and caucuses.

In all of 1975, candidate Jimmy Carter raised less than $1 million; in the single month of May, 1976, after a string of victories from New Hampshire to Pennsylvania, he raised $2.7 million. Similarly, in February, 1980, after his upset victory in the Iowa caucuses, George Bush raised $2.5 million.

The 1984 primary calendar with its heavy "front loading"--about 50 percent of the delegates will be chosen by the end of March--means that there will be little time for early winners to cash in on their triumphs.

"The real key is going to be how much cash on hand the candidates have by Jan. 1, when they'll want to be able to start spending it heavily," said William Oldecker, a veteran presidential fund-raiser. "Early money is more important this time out than ever before."

Mondale is envied for that reason. He's the front-runner; he's run for national office before; he has a money network in place.

According to Federal Election Commission reports, Mondale raised $2.4 million in the first three months of 1983, more than twice as much as anyone else, and he finished the quarter with $737,263 cash on hand.

The first-quarter figures for the others: Sen. John Glenn (D-Ohio) raised $1.2 million, with $500,036 cash on hand; former governor Reubin Askew of Florida, $809,377, with $524,095 left; Hart, $465,266, with $25,684 left; Cranston, $457,653, with $36,465 left, and Sen. Ernest F. Hollings (D-S.C.), $246,762, with $11,349 left.

Mondale, like Hart and Askew, refuses to accept political action committee funds. All three find PACs more valuable as whipping boys.

One reason for this attitude is that no presidential candidate has ever gotten more than 3 percent of his funds from PACs, which prefer to concentrate on congressional races.

With PACs off limits, with the big bankrollers of yore, such as Clement Stone and Stewart Mott, legislated out of the game, presidential fund-raising has become a middleman's game. Mondale's treasurer and long-time political adviser, Mike Berman, has a name for who he's after: "thin cats."

"Some of the heavy shooters almost think it's beneath their dignity to make $1,000 fund-raising calls," says Wanning, a professional political fund-raiser who's worked for Sen. Edward M. Kennedy (D-Mass.) and former senator John C. Culver (D-Iowa). "What you wind up going after are 50 people who can raise $10,000 apiece, not 10 people who can raise $50,000 each."

That translates into phone calls, phone calls, phone calls. Wanning works for Hart from every Democratic political list he can get his hands on, and lots of the time he's calling people blind.

Hart starts out with a disadvantage: He hails from Colorado, hardly a Democratic money mecca, and early money generally comes from the candidate's base.

Thus, a longshot like Askew can make a strong early showing because he's from the monied state of Florida. Similarly, Cranston and Glenn got about half their early money from their well-endowed states of California and Ohio.

Mondale's base is national.

Coming from South Carolina, Hollings has the same problem Hart does.

But all work hard in the Big Five money states--New York, California, Illinois, Texas and Florida.

All, too, are going after contributions from the Jewish community, which has been underwriting Democratic primary politics seemingly since the beginning.

"The Jewish community is almost like a big law firm," Wanning says. "It seems to have someone in everyone's camp. Sometimes you almost feel like you are getting your assignee."

Of the six Democratic presidential candidates, Mondale, Glenn and Cranston are considered strongest in the Jewish community.

Cranston is identified with the nuclear peace issue, which historically has been of particular concern to Jews, and many Jewish contributors are concentrated in California. Mondale has a long pro-Israel record. Glenn's national finance chairman is Milton Wolf, a former ambassador to Austria and a Jewish philanthropist from Cleveland.

The other principal source of primary funds is direct mailings. They are now a staple of all political campaigning, but they have special appeal in a presidential primary for a couple of reasons.

One is that mail money tends to come in small amounts--$25 is the average--and therefore qualifies for federal matching funds.

Another is that the high cost of direct mail is less of a concern for presidential candidates in the primaries. They are permitted by law to spend a fixed amount on the campaign itself--depending on the inflation factor, about $20 million in the 1984 primaries, with the general election fully financed by public funds--plus 20 percent for the cost of fund-raising.

There are several interest groups Mondale can appeal to by mail. In addition, in 1982 he had his own candidate PAC, which raised more than $2 million for his travels and for contributions to congressional candidates. The PAC now provides him with a proven mailing list.

Hart is about to go into the mails with a test of his "new agenda" campaign themes. Cranston has already mailed to past givers and to nuclear freeze advocates.

"For the first time in my life I actually did better than break even on a prospecting sample," says finance director Muyskens, who came to the Cranston campaign after fund-raising for the Wilderness Society and Yale University.