The longest, costliest, most controversial corporate power struggle Washington business has ever seen is just two days away from a showdown.

The annual stockholders' meetings of Financial General Bankshares Inc. on Wednesday in Richmond is expected to determine once and for all who will run the local chain of First American banks and their affiliates in two other states.

If Financial General's management can win a mandate from the stockholders, Chairman B.F. Saul II and President J. William Middendorf II should be formly in control of the $2.3 billion bank firm.

But if three insurgent candidates win seats on the board of directors or an anti-management resolution is passed by the shareholders, Saul and Middendorf could be forced to make a deal with the Middle Eastern investors who have been trying for 2 1/2 years to buy control of the bank holding company.

Even a narrow victory for management could weaken the company's opposition to the takeover and increase the pressure for a settlement with the group lead by Sheik Kamal Adham of Saudi Arabia.

The two sides came close to a compromise a few days ago, but the deal broke down, with an offer of $28.50 a share on the table. The stock was a big percentage gainer last week, up 23 percent to $21.50 and near its 52-week high. The Middle Eastern group started buying when the shares were less than $15.

Most shareholders who've owned stock since before the takeover fight began in December of 1978 bought it for between $5 and $13 a share. A buy-out at $28.50 would allow them to at least double their money, and perhaps get back four or five times what they've invested.

Saul and Middendorf's response to those tempted to sell has been to insist that an unfriendly foreign takeover cannot win the approval of state and federal banking regulators, and for 2 1/2 years they've proved themselves right.

Already each side is said to have spent considerably more than a million dollars on lawyers. Soliciting votes for this year's annual meeting has proved to be as costly as a campaign for Congress, with the total price expected to exceed $500,000.

The meeting is set for 10 a.m. Wednesday at the Richmond Hyatt House.