Democratic campaign strategists hope they have found a way to hamstring the National Conservative Political Action Committee.

It's called "The Finkelstein Connection."

The "connection" is named after Arthur J. Finkelstein, a New York pollster and political consultant who works for conservative Republicans.

The Finkelstein Connection has surfaced in NCPAC's early-starting campaign to defeat Sen. Daniel Patrick Moynihan (D-N.Y.), one of the committee's most prominent targets in 1982.

Democrats hope the challenge to Moynihan will put NCPAC's future on the line. If the Democrats can prove that NCPAC is working for Bruce Caputo, a Republican former congressman who is challenging Moynihan, it could lose its status as an "independent" committee. This status enables it to spend unlimited amounts to elect or defeat candidates, which is what has made it a fearsome factor in recent elections.

Federal Election Commission rules allow independent committees--those that have no communication or coordination with a candidate or his supporters--free rein on political spending, as opposed to the $5,000 limitation put on other political action units. NCPAC is registered as an independent committee.

Under FEC rules a violation--a determination that an independent committee has coordinated with a candidate or campaign organization--can cost the committee its independent status and a civil penalty of up to twice the amount of its illegal contribution. In the Caputo case that could come to as much as $200,000 for NCPAC.

NCPAC insists it is trying simply to defeat liberal incumbents, with whom it lumps Moynihan, not to elect individual conservatives, such as Caputo.

But the Democrats think it is more than coincidence that Finkelstein's firm is listed as "campaign consultant" in Caputo's latest report to the FEC. Also:

Finkelstein has been a member of the NCPAC board of directors, although a committee spokesman says he resigned two or three years ago.

Of the $19,500 that Caputo had spent on his fledgling campaign through July, $12,300 went for Finkelstein's polls and political advice.

NCPAC's August filing with the FEC showed a $4,400 contribution to the Caputo campaign.

Terry Dolan, NCPAC's chairman, says Finkelstein is playing an important part in the organization's activities. In a Nov. 17 press conference in New York City, he said Finkelstein was responsible for NCPAC's polling in New York as well as nationally.

Some NCPAC ads have segments that appear to have been taken word-for-word from Caputo's formal announcement of his candidacy, and from a fund-raising letter signed by Caputo and now being circulated in New York.

NCPAC spokesman Steve DeAngelo says NCPAC is not talking to Finkelstein "on a daily basis or even a weekly basis" and as soon as Caputo is nominated the connection will be severed.

According to DeAngelo, the FEC has ruled that an independent committee cannot be charged with working for a candidiate until he has been formally nominated. Caputo has not yet won the nomination, although he has the endorsement of 50 of the 62 Republican county chairmen in the state and apparently has no opposition for what many observers consider the uncertain honor of running against Moynihan.

The Democrats contend that this FEC ruling has been modified and that the FEC now says there can be no pre-primary links between an independent political committee and a potential candidate.

The FEC says that both are wrong, and that it has only advised NCPAC that the closer an independent committee gets to a candidate the more its chances of compromising its independence.

NCPAC has budgeted $750,000 to defeat Moynihan, with $50,000 of that for a "first wave" of television commercials.

The Democrats, through their national, Senate and House campaign committees, are considering suing NCPAC on the ground that it is working for Republican candidates, including Caputo, and therefore is not an "independent" committee.

FEC rules state that a political expenditure is not "independent" if made by a person "receiving any form of compensation or reimbursement from the candidate" or any "agent" of the candidate.

The Democrats contend that Finkelstein is clearly a Caputo "agent" and that NCPAC's moves in New York appear based on information about Caputo plans provided by Finkelstein. Such an information link is a big no-no for an "independent" political committee.

Democratic strategists call the $4,400 NCPAC gift to Caputo a "remarkable early commitment." NCPAC, however, also gave Caputo money for his losing 1980 campaign against incumbent Jacob K. Javits for the Republican Senate nomination. The nomination went to Alfonse M. D'Amato, who was elected.

The Democrats also will focus on comments by White House political adviser Edward Rollins that he expects to be working closely with NCPAC on the 1982 campaign, which would involve electing Republicans rather than just defeating Democrats.

Ironically, the Democrats have managed to shake loose a Finkelstein poll that shows Moynihan with a 3-to-1 lead over Caputo. Of 879 persons polled, 48 percent backed Moynihan, 16 percent supported Caputo and nearly 36 percent were undecided.