NEW YORK (CNN/Money) - The war of words between Hewlett Packard Co. Chairman and CEO Carly Fiorina and dissident Walter Hewlett could come to an end Tuesday when HP shareholders will vote on the $21 billion merger. But a final outcome may be weeks away.

HP shareholders will meet Tuesday in Cupertino, Calif., to vote on the Compaq takeover. Dissident Hewlett is expected to make a speech, while Fiorina will take part in a "question and answer" session. The vote, which will start at 8 a.m. PT (11:00 a.m. ET), is expected to last throughout the day.

Compaq shareholders will make their decision on Wednesday.

"It's going to take a couple weeks to get a decision but both sides will declare victory tomorrow," said influential analyst Andy Neff of Bear Stearns.

And the vote could take on Floridian proportions. IVS Associates, the firm that will collect the proxies and determine the final outcome, will give the parties a chance to review and challenge the tally. Once IVS has ruled on all of the challenges, it then certifies the vote.

"We feel positive and think the momentum is on our side that strategic logic [of this merger] will be appreciated," said Compaq spokesman Arch Currid. "But we will likely not know tomorrow."

HP could not be reached for comment Monday. But HP's Fiorina and Compaq CEO Michael Capellas were each lobbying shareholders and customers Monday to vote for the deal, Currid said.

A spokesman for dissident Hewlett, who has waged a bitter proxy battle to stop the merger, said the vote was still too close to call. "We just don't know right now but we feel really good about our numbers today," the spokesman said.

HP has attempted to depict Hewlett as an "artist and musician," while Hewlett has tried to paint Fiorina as "conflicted" and trying to get a huge compensation package. Analysts and observers have said that if the merger failed, Fiorina would likely depart as well.

Shares of both HP (HWP: Research, Estimates) and Compaq (CPQ: Research, Estimates) gained marginally Monday.

The HP-Compaq merger scored some triumphs this month. Influential proxy advisory firm Institutional Shareholder Services backed HP's takeover of Compaq. ISS clients control 23 percent of HP shares, and many are expected to follow ISS's guidance. The Federal Trade Commission also cleared the merger without conditions.

HP Director Phil Condit said last week that the computer maker had secured the support of most of its 20 largest shareholders. But Walter Hewlett has rallied several institutional investors, including the California Public Employees' Retirement System, or CalPERS, against the transaction.

HP investors line up to cast their votes.

Even though most HP shareholders have already voted, Tuesday's meeting is expected to be the curtain raiser on a drawn-out process. Institutional investors hold roughly 57 percent of HP's stock. Retail, or individual, investors hold about 25 percent, while management and insiders own less than 1 percent. Analysts said Monday that the swing vote could come from retail investors.

Hewlett, the son of one of HP's co-founders, together with other descendents of the founding partners, control roughly 18 percent of HP's voting shares. The dissident is expected to get some support from retail investors taking a "David and Goliath" approach to the merger and siding with Hewlett

"HP has not been soliciting retail investors," one analyst said, who declined to speak for the record.

The outcome of the merger could also rest on the decision of two large shareholders. Capital Research & Management and State Street Global Advisors together hold a near 6 percent stake in HP, data from Thomson Financial said. However it is unknown how either institution will vote.

State Street owns 2.1 percent of HP while Capital Research has a 3.5 percent stake. State Street, an index fund that holds a representative basket of securities, is expected to vote with management. Capital Research may also support the deal, as it has been buying Compaq shares since the HP-Merger was announced last September, analysts said.