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As a shareholder vote on the proposed buyout of Dell Inc. approaches, its founder, Michael S. Dell, and the investment firm Silver Lake are standing firm, not raising their $24.4 billion offer.

While they strongly believe that their bid of $13.65 a share is full and fair, the two also appear to be staring down Institutional Shareholder Services, the biggest proxy advisory firm.

I.S.S. is likely to publish its recommendation on the management buyout, which shareholders will vote on July 18, within the next week. Advisers to both the buyers and to a special committee of Dell’s board assume that the report is likely to be unfavorable to the deal, potentially dealing a huge blow to its chances of success. That, however, could serve the interests of Mr. Dell and Silver Lake.

Mr. Dell, who owns a 16 percent stake, is trying to take the company private, and is facing an alternative proposal by the billionaire Carl C. Icahn and the asset management firm Southeastern Asset Management. Their proposed buyback of 1.1 billion shares at $14 each values Dell at about 12 times earnings before interest, depreciation and amortization.

Mr. Dell and Silver Lake believe that Dell’s stock will tumble if I.S.S. comes out in opposition to their deal, as investors fear that the transaction will fail and flee the stock. A significant portion of the shareholder base — by some counts, more than 15 percent — is held by arbitrageurs who are betting on the success of the leveraged buyout and are inclined to bail out if signs emerge that the takeover is on the rocks.

There already appears to be a hint of that phenomenon: the company’s shares fell more than 4 percent on Friday after reports from The New York Post and Bloomberg News said that the buyers intended to stand firm on their bid. Dell stock closed down 2.10 percent for the day, at $13.03.

That drop, however, may serve to help the buyout offer. People close to both them and to the Dell special committee are betting that I.S.S. may still be swayed to support the deal if the company’s stock plummets in the wake of the transaction’s failure.

The Dell special committee published a supplemental investor presentation on Friday that further painted a gloomy picture of the company’s future if the deal does not succeed. The materials were produced to answer questions from I.S.S. about how a stand-alone Dell’s shares might trade if the deal fails.

The committee, which has already encouraged Mr. Dell to raise his offer to save the company, also pointed to analyst price targets for Dell’s stock before word of the leveraged buyout emerged. Analysts generally estimated that the company would trade at about 7.2 times earnings for the 2014 fiscal year. At current earnings estimates of $1.04 a share, that would mean that Dell is expected to trade at about $7.49 a share.

Mr. Icahn has argued that the company is overstating its state of financial duress. One sum-of-the-parts estimate he has put forward on Dell is about $22.34 a share.