The 1986 campaign cash spigot has been turned wide open in the 17 most contested Senate races, with an average of over $1 million channeled into each race during the past three months alone.

The flow of money reached the highest levels in California, where incumbent Sen. Alan Cranston (D) raised $914,578 and his challenger, Rep. Edwin V.W. Zschau (R), $1.02 million in just 1 1/2 months.

California remained at the top of the Senate fund-raising list, with Cranston's cumulative total reaching $5.6 million, and Zschau's $2.7 million. Cranston goes into the final four months of the campaign with a significant advantage in his bank balance, $1.4 million compared to Zschau's $444,802.

Florida is running a close second to California, as Gov. Bob Graham (D) raised $1.3 million during the past three months in his bid to oust Sen. Paula Hawkins (R), who pulled in $731,740. Graham and Hawkins have both raised just over $3.5 million, although Graham had $1.6 million in the bank as of June 30, while Hawkins had $828,887.

The cost of running for the Senate has been steadily rising. In 1980, the average candidate spent $1.1 million; in 1982, $1.7 million; and in 1984, $2.1 million, according to Federal Election Commission figures as compiled by the Center for Responsive Politics.

This year, there are 34 Senate elections, but most experts believe that about 17 now appear to have the potential of turning into close contests. In the list of 17 developed by The Washington Post, Republicans had a significant money advantage in nine, Democrats in five, and three contests were financially close.

Close races are the terrain where money can determine the outcome. In 1982, five Senate races turned out to be very close, and Republicans won each of them. One factor in those victories was the GOP candidate's ability to finance, in the final weeks of the campaign, highly expensive daily tracking polls permitting the candidate to make last-minute changes in television commercials, scheduling and other campaign activities.

As the candidates enter the final months of campaigning before Election Day, Nov. 4, one of the key figures in their finance reports is "cash on hand," indicating the amount of money each has to finance the most expensive period of the contest.

From this vantage point, Republicans are heading into the decisive period of the campaign with a strong edge over their Democratic opponents. In nine states -- Louisiana, Washington, Missouri, Wisconsin, Idaho, Alabama, Oklahoma, North Dakota and Pennsylvania -- the Republican candidate has a cash balance advantage.

In four of those states, each of which has an incumbent Republican, the GOP advantage exceeds 10 to 1: in North Dakota, Sen. Mark Andrews has $660,487 compared to tax commissioner Kent Conrad (D) $62,495; Pennsylvania Sen. Arlen Specter has $1.7 million to Rep. Bob Edgar (D) $105,956; Washington Sen. Slade Gorton has $821,141 to former representative Brock Adams (D) $74,383, and Wisconsin Sen. Robert W. Kasten Jr. has $1.2 million compared to likely challenger Ed Garvey (D) $71,741.

The only case where the Democratic cash margin reaches such heights is in Vermont, where Sen. Patrick J. Leahy (D) has $598,472, compared to former governor Richard A. Snelling (R) $36,830.

South Dakota is the only state where an incumbent Republican senator, James Abdnor, has raised less than the Democratic challenger. Rep. Thomas A. Daschle (D) continued to outpace Abdnor, $560,020 to $210,229, bringing his total to $1.7 million, compared to Abdnor's $1 million.

While the Democrats are generally running behind their Republican opposition, some of the Democratic candidates are showing signs of gaining financial muscle.

In Oklahoma, Rep. James R. Jones (D) raised more money during the past three months than Sen. Don Nickles (R), just as Missouri's Harriett Woods (D) raised more money in the same period than former governor Christopher S. Bond (R), although both Nickles and Bond have significant financial advantages overall.

Similarly, such financially beleaguered Democrats as Edgar in Pennsylvania, Idaho Gov. John V. Evans and Rep. John B. Breaux in Louisiana almost equaled their Republican opponents in the most recent reporting period, after running far behind earlier in the race.

In a contest receiving national attention, however -- North Carolina -- GOP Rep. James T. Broyhill has expanded his cash lead over former governor Terry Sanford, raising $1 million from April 17 through June 30, compared to Sanford's $433,490.

In the Georgia Democratic primary fight between Rep. Wyche Fowler Jr. and Hamilton Jordan, former chief of staff to President Jimmy Carter, Fowler reported a June 30 cash balance of $606,743 compared to Jordan's far smaller $86,821. The winner of the contest will face Sen. Mack Mattingly (R) who is sitting on $829,959 in the bank.

In an entirely separate series of FEC reports, Vice President Bush continued to hold a commanding lead among prospective Republican presidential candidates. His political action committee, the Fund for America's Future, reported total fund-raising of $8.3 million, including $352,341 in the last month.

The PAC run in behalf of Rep. Jack Kemp (R-N.Y.) has raised a total of $2.3 million, including $208,162 in June. The Committee for Freedom, the PAC tied to television evangelist Marion G. (Pat) Robertson, raised $295,419 in June, for a total of $540,304 in the two months of its existence.

The PAC of former Senate majority leader Howard H. Baker Jr. (R-Tenn.), the Republican Majority Fund, raised $80,173 in June, while Campaign America, the PAC of current Senate Majority Leader Robert J. Dole (R-Kan.) raised $253,259 in June.

The one Republican to formally declare his presidential candidacy, former Delaware governor Pierre S. du Pont IV, reported that his presidential committee raised $168,315 from June 3, when it was founded, to June 30.

On the Democratic side, Americans for the National Interest, the PAC set up by Arizona Gov. Bruce Babbitt, raised only $195 in June, raising its two-year total to $101,078. The Effective Government Committee, set up by Rep. Richard A. Gephardt (D-Mo.), raised $292,238 in June.