"The number of shares owned by institutions that have publicly indicated their support for the merger is about double that of those that have indicated they are opposed, excluding shares owned by the Hewlett and Packard families and the foundations associated with them," HP said in a statement.
Meanwhile, dissident board member Walter Hewlett countered that he also has some big-name backers, as well as the support of many individual investors.
HP and Compaq announced their intentions to merge last September in a deal initially valued at $25 billion.
But the past six months have been marked by a series of caustic statements by proponents and opponents, each touting the merits of their position while disparaging their critics. As HP shareholders prepare to cast their votes on Tuesday, each side has attempted to show that it is building momentum by trumpeting the names of the large shareholders they count as backers.
According to HP, more than 20 institutional shareholders have disclosed that they plan to support the buyout. It cited Alliance Capital, Banc One Investment Advisors, Barclay's Global, Collins & Co., Domini Social Investments, Federated Investors, Fremont Investment, General Motors Investment Management, Intel, ITUG, Interex, L. Roy Papp Associates and Putnam Investment.
"In addition, in the last 48 hours," HP added, "four big retirement funds--Florida State Board of Administration, Pennsylvania Public School Employees Retirement System, State Teachers Retirement System of Ohio and the Wisconsin Investment Board--have stated their intent to vote in favor of the merger."
The computing giant conceded, however, that investors that have publicly announced their intentions represent only a portion of the total outstanding shares, meaning that "HP cannot predict the outcome of the vote until all votes are in."
While HP is tallying its backers, opponents--led by Hewlett--have also gained key votes in the past week.
On Friday, for example, the New York State Teachers Retirement System Pension Fund and the New York State Pension Fund said they will vote against the deal. Including the "no" votes already pledged by Hewlett and Packard family members and their investment trusts, opponents control about 24 percent of HP's outstanding shares.
In a press release late Sunday, Walter Hewlett claimed support from about 55 percent of registered shareholders, defined as those who own shares on their own rather than through a broker or fund.
Such shares make up a small fraction of all HP shares, with Hewlett's camp putting the number at about 5 percent of all shares. Even within that group, the result is not definitive because shareholders can vote multiple times with only their last votes counting.
Additionally, Hewlett's camp only has access to green proxies and not to the white proxies being distributed by HP. However, to the degree to which it is indicative of how individual investors feel, it could be significant as such investors could end up being decisive in this race, which experts say is too close to call.
Hewlett's camp also touted support Sunday from a variety of institutions, including Northstar Asset Management and Safeco Asset Management, as well as a number of prominent pension funds that came out publicly last week.
As is to be expected, HP responded late Sunday to Hewlett's release, essentially saying his math is wrong.
"Claims made today by Hewlett regarding the registered holders voting on his green proxy card mischaracterize the actual vote of HP shareowners," the company said in a press release. "Shares owned by record holders (excluding the Hewlett and Packard interests) represent less than 3 percent of the total shares entitled to vote at the special meeting."