Former governor Tom McCall, considered one of this state's most popular and best known public figures and a nationally known supporter of environmental causes, received an unexpectedly stiff challenge in the closing days of his quest for the Republican nomination for governor.

A recent poll by the Portland Oregonian showed McCall leading in the three-way race which will end in today's voting. But state Sen. Victor Atiyeh, who was the Republican gubernatorial nominee four years ago when the Oregon constitution barred McCall from seeking a third consecutive term, came in a close second. A third candidate, state Rep. Roger Martin, House minority leader, trailed by a sizable margin.

Since McCall left office four years ago, he has maintained high popularity in public opinion surveys, and has been widely considered almost certain to win the primary and face Democratic Gov. Bob Straub in the November general election. Straub beat Atiyeh four years ago after losing twice to McCall, and has only token opposition in the Democratic primary.

McCall's colorful specking style and admonition to visit Oregon "but for heaven's sake don't come here to live" drew national attention to his support of environmental causes.

But traditionally he has received much of his support from Democrats and independent-minded voters and could have less appeal in a primary to Republicans who are equally divided between conservative and moderate voters here. The party was almost evenly split between President Ford and Ronald Reagan in the 1967 GOP primary, with Ford winning by a slight margin.

When McCall announced he would seek a third term, many political observers speculated that Atiyeh and Martin would split the anti-McCall vote, giving the former governor an easy victory. They each rejected efforts to persuade the other to drop out to give the party a clear choice for or against McCall. Oregon has a closed primary, with no provision for a runoff or crossover voting.

The poll conducted for the Oregonnian showed McCall supported by 42 percent of the sample compared to 28 percent for Atiyeh and 14 percent for Martin. In a more important group - those considered most likely to vote - however, McCall led Atiyeh by 6 percentage points, 38-to-32 percent. The poll had a 5 percent margin for error. Entering the race in February, McCall had predicted he could only drop in the polls since he was starting with such a high rating.

The state's elections office has predicted 45.5 percent of the registered woters will go to the polls, which would be the lowest primary turnout in the state's history.

The campaigns of the three candidates - which included three joint appearances - have focused on their differing styles and philosophies rather than specific issues.

McCall has emphasized his record as governor for eight years but tempered his support of environmental protection with the admission that some state agencies have unnecessarily harassed business.

Martin has appealed to rural, conservation voters, promising to reduce the size of the state bureaucracy. He also has subtly attacked McCall by saying that at age 65 McCall should not be given another term. Martin also has blamed McCall's administration as governor for major increases in the state budget.

Atiyeh has avoided personal clashes and focused on his 20 years' experience as a legislator, portraying himself as the moderate in the race.

Oregon's constitution limited McCall to two consecutive terms, but he is eligible to hold office again after sitting out a term.

Other primary races have drawn little interest. U.S. Sen. Mark Hatfield (R-Ore.) is expected to easily win the Republican nomination for a third term, although an eastern Oregon cattle rancher, Bert Hawkins, has been campaigning in recent weeks seeking conservative Republican support.

Of the four U.S. House members, all Democrats, only Rep. Jim Weaver has primary opposition, and he is expected to win nomination to a third term.