In an attempt to exploit the Panama Canal treaties as a partisan issue, the Republican National Committee has enlisted Ronald Reagan to spearhead a massive mail campaign aimed at raising $2 million from treaty opponents.

The committee is preparing to send a six-page fund-raising letter, written and signed by the former California governor, to between a half million and a million people on its mailing lists.

In the letter, the influential political conservative attacks the treaties as a surrender of vital U.S. strategic interests and calls for an all-out effort to block their approval by the Senate.

The letter asks arecipients to sign enclosed petitions opposing the treaties and to contribute "a minimum of two million dollars" to the Republican Party.

"Unless these funds are raised," Reagan writes, "we won't defeat those Democrats who vote time and time again to support actions that weaken our national security . . . Believe me, without your support, the canal is as good as gone."

In trying to use hostility toward the treaties as a device for soliciting funds, the committee appears to be taking the canal debate into a partyline fight between Republicans and Democrats.

That course has been urged by the Republican Party's conservative wing, which sees the emotions generated by the proposed transfer of the canal to Panamanian control as the most effective issue to come along so far in the Carter administration.

Party moderates, mindful both of former President Ford's support of the treaties and of President Carter's pleas that they be considered in an atmosphere of bipartisanship, have been trying to sheer the party away from outright identification with the anti-treaty campaign.

But the moderates seem to have been losing this internal struggle. At its Sept. 30 meeting in New Orleans, the 162-member national committee adopted a resolution condemning the treaties. Its only concession to the moderates was to sidestep a direct repudiation of Ford by declaring that it opposes the treaties "as proposed by President Carter."

Now, the committee appears to be going a step further by enticing Reagan back into the controversy. Although Reagan is against the treaties, he so far has disappointed those who had wanted him to assume the symbolic leadership of the forces seeking to block the two-third Senate vote needed for their approval.

Except for an appearance before a Senate Judiciary subcommittee in early September, Reagan has kept largely to the sidelines. He refused an invitation to testify before the Senate Foreign Relations Committee earlier this month, and he was conspicuously absent from the cast of prominent treaty opponents appearing in a TV propaganda film made recently by the American Conservative Union.

Now, his signature on the national committee's anti-treaty letter is likely to give party conservatives a big boost in their campaign to make the canal debate a partisan issue.

Soliciting funds is the name of fighting the treaties is bound to increase the pressure on such Republicans as Senate Minority Leader Howard H. Baker of Tennessee, who is undecided about how he will vote. To go against his party's increasing indentification with the anti-treaty forces would make it more difficult for him to become a presidential candidate in 1980.

Republican National Chairman Bill Brock defended the Reagan letter yesterday as "a legitimate appeal to many Republicans and others who are deeply concerned about the canal issue."

Brock, who estimated the cost of mass-mailing the Reagan letter at approximately $200,000, denied that it "necessarily favors one faction of the party over another."

It is the national committee's policy, Brock said, to invite leading Republicans to send out fund-raising letters based on issues "that are in the forefront of their personal concerns, and Gov. Reagan chose to address himself to the canal question in this instance."

In the past, Brock noted, similar appeals for funds have been sent out by Ford. "I forget right off hand what subjects he chose to base his appeals on, but he had the same latitude of choice," Brock said.

Although "the majority of Republicans, in the Senate and elsewhere, seem opposed to the treaties," Brock said, "the opposition isn't totally partisan, and it's really too early to say whether opposition is going to be an identifiably Republican issue in next year's congressional elections."