Rep. Richard A. Gephardt (D-Mo.) was in Washington last night, Sen. Paul Simon (D-Ill.) in New York, Sen. Albert Gore Jr. (D-Tenn.) in Dallas. Each was pausing in his quest for votes to search for the other main commodity of politics: money.

The fund-raising efforts are especially vital for Gephardt and Simon, who spent heavily in Iowa and have little money in the bank. Democratic rivals Gore and Massachusetts Gov. Michael S. Dukakis, in contrast, have sizable bankrolls.

Gore had about $2.7 million at the start of the year, skipped the spending frenzy in Iowa and is the beneficiary of a Dallas fund-raiser that Texas financier Jess Hay said yesterday was expected to raise $700,000 to $800,000.

Dukakis had $6 million available to start 1988 and his chief fund-raiser, Robert Farmer, said yesterday the major fund-raising won't begin until after Tuesday's New Hampshire primary. "I'm having just a little $100,000 dinner at my house tonight," he said. ". . . The candidate won't even be there."

In 1984, surprising finishes in Iowa and New Hampshire propelled Gary Hart into the spotlight and provided him a financial windfall. His contributions jumped from $125,000 in January of that year, to $342,000 in February, to $3 million in March, before starting to decline.

The New Hampshire spending limit is $461,000, the lowest of any state. So the question is whether Gephardt or Simon can break out of the Democratic field enough to raise money to compete effectively with their rivals in the March 8 "Super Tuesday" sweepstakes.

Farmer said he thinks that it is "physically impossible" after New Hampshire to collect funds, process checks and get federal matching funds in time to buy television air time for Super Tuesday. "This puts a premium on those who are fortunate enough to raise money early and conserve it," he said.

The first tier of Republican candidates is in better financial shape, with Vice President Bush having an $11 million cushion at the start of the year and Sen. Robert J. Dole (R-Kan.) nearly $7 million. Pat Robertson had enough funds to pay off a $1.5 million bank loan last month without touching $6.5 million in matching funds, according to a campaign official.

Rep. Jack Kemp (R-N.Y.), who has raised $7 million in donations -- the fourth-largest amount among GOP candidates but more than any Democrat except Dukakis -- has a contributor base 100,000 strong but little cash on hand. He also finished fourth in Iowa, however, and his aides say that if he doesn't break into the top two in New Hampshire there will be little reason to go back to his supporters to ask them to write another check.

Not surprisingly, Gephardt and Simon fund-raisers are upbeat about their candidate's prospects. Boyd Lewis, finance director for Gephardt, said yesterday he's pleased with the response to his candidate's first-place finish in Iowa. "We're in the mail; we're on the phones," he said. "We call it the New Hampshire blitz."

Lewis said the campaign called more than 100 supporters around the country after Iowa, asking them to raise $2,000 to $5,000 each and air-express the money to Washington so it can be used for media purchases for New Hampshire. The campaign also borrowed $40,000 this week against expected matching funds to buy more television time.

He predicted the campaign would raise about $75,000 at last night's $500-a-plate dinner here at the Hyatt Regency. The event was planned hurriedly last week. And Gephardt, who campaigned in Iowa with a populist theme, was on hand to collect the checks of the same Washington insiders he has criticized.

Tonight he goes on to a small dinner at the Helmsley Palace Hotel in New York City, which is expected to raise another $50,000, Lewis said.

Because of the short length of time between New Hampshire and Super Tuesday, Lewis said, the Gephardt campaign is concentrating on using the telephone, rather than direct mail, to reach new donors.

Bob Edgar, Simon's national finance director, said yesterday that proceeds from his candidate's New York dinner (an expected $100,000) and another round of small fund-raisers in Chicago next week (a hoped for additional $150,000) will go toward campaign expenses in such post-New Hampshire states as Minnesota and South Dakota.

A Simon spokesman said the senator has borrowed $110,000 this week to pay for radio and television advertising in New Hampshire.

Nancy Kuhn, Simon's New York finance chairman, said yesterday that response to last night's dinner at the Ritz Carlton had been "flat" as "people were waiting" to see how Simon did in Iowa. Since Monday, she said, 3 1/2 10-seat tables were added, assuring a capacity crowd.

Edgar noted that the campaign also invested $20,000 in a mailing of 48,000 telegrams to Simon supporters Tuesday, the day after the Iowa caucuses. "We anticipate getting back $150,000," he said.