DULUTH, Minn. (AP) _ Deeply divided Republicans cast 14 ballots over two days yet could not agree to endorse either Rudy Boschwitz or a more conservative candidate for his old Senate seat Saturday.

The rift between moderate and conservative elements of the party is threatening to derail the GOP's efforts to unseat Paul Wellstone, a liberal Democrat.

Bert McKasy, a former state commerce commissioner and legislator, came close but never mustered 60 percent of the delegates, or 1,209 votes, needed for the endorsement.

As a result, it would be more difficult for McKasy to defeat Boschwitz in the Sept. 10 Republican primary, since an endorsement is a strong recommendation and also means financial backing from the party.

McKasy, however, has not committed himself to running in the primary, and said Saturday he will make a decision within the next few days. State Senator Roy Terwilliger has said he definitely will run.

The vote not to endorse any candidate came after 14 ballots over two days, with McKasy winning as much as 56 percent of the votes in one of those ballots.

After the initial round of voting ended at 3:30 a.m. Saturday, delegates returned mid-morning and the final vote came shortly before 4 p.m.

``I never thought we'd have a convention where delegates did not endorse,'' said Leon Oistad, a former party chairman.

McKasy has generally run to the right of Boschwitz, who served in the Senate from 1979 until he was upset by Wellstone in 1990. Wellstone at the time was a little-known political science professor.

Boschwitz backers believe he has the best shot at defeating Wellstone in November.

Delegate Gerald Goldschmidt said Boschwitz would appeal more than McKasy to the ``mildly conservative'' voters that Republicans need to win the election.

Known as Minnesota's plywood king for founding Plywood Minnesota, a chain of do-it-yourself stores now named Home Valu, he also tries to cultivate a folksy image with flannel shirts and a milk stand at the State Fair.

Although McKasy supports voluntary prayer in schools and has defended right-wing presidential contender Patrick Buchanan, some observers maintain the two candidates are equally conservative.

``You have a situation where the two leading candidates are, philosophically, virtually identical,'' said Allen Quist, a farmer and leader of the party's social conservative faction.

McKasy, 53, who was considered the favorite heading into the convention, worked harder for support of GOP activists.

While far better financed than McKasy and much better known among voters, Boschwitz, 65, had all but conceded the endorsement prior to the convention. He angered some party activists by announcing that he would seek the GOP nomination in the primary regardless of who won at the convention.

The battle within the state GOP comes after a similar situation two years ago, when the state convention backed Quist over the more moderate Gov. Arne Carlson for the gubernatorial race. The governor went on to defeat Quist in the primary and win re-election. Commentators have said that situation was much more bitter than the current split, however.

Also seeking the Senate endorsement were Monti Moreno, who owns a hair salon; John Herman, a former newspaper publisher, and Terwilliger.

All three were out of the balloting by the third round Friday night.