The possibility of Barack Obama becoming the next President of the United States could lead to a takeover spree in the next six months as companies look for deals before his proposed tax changes.

Mr Obama, the presumptive Democratic presidential nominee, has indicated that he wants to raise capital gains tax to pay for his expansion of healthcare and this could hit families that want to sell their companies.

Louis Capital Markets (LCM), a New York investment firm, said yesterday that concern about higher capital gains taxes could trigger a spate of deals.

The firm's analysis came as Rohm and Haas, a family-controlled paints and materials company, was bought by Dow Chemical for $18.8 billion (£9.5 billion), including debt.

The Haas family trusts, which own 33 per cent of the company, accepted an all-cash offer that was 74 per cent higher than Wednesday's share price.

Dow's bid has been backed by the Kuwait Investment Authority and Berkshire Hathaway, which is controlled by Warren Buffett. The purchase of Rohm and Haas will give the Michigan chemical group a strong portfolio of higher margin products.

The acquisition of Wrigley's, the chewing gum maker, by Mars for $23 billion this year is another example of a family-controlled company selling up.

LCM said that it expected more family-owned companies to be sold in coming months, including Marriott Hotels and Estée Lauder, the cosmetics company. The Lauder family owns 58 per cent of the company and 90 per cent of the voting stock. LCM has identified Procter & Gamble and L'Oréal as potential buyers.

Mr Obama has also indicated that he will strengthen antitrust rules, which could limit the deal-making opportunities in markets where there are a limited number of competitors.

Deutsche Telekom, which owns T-Mobile, is thought to be interested in expanding its US presence with a bid for Sprint, the mobile phone operator, and may move sooner rather than later to beat changes in competition rules. AT&T, Verizon, Sprint and T-Mobile control 92 per cent of the US market and while further consolidation may be allowed by the current Bush Administration, it may be frowned on by an Obama White House.

Analysts at LCM said: “We expect that more companies with large family stakes will try to sell themselves and that more consolidation in highly concentrated sectors may transpire before the new President takes office.”

US betting firms say that there is an 65 per cent chance that Mr Obama will become the next President.

LCM's analysts added: “Although the outcome of the presidential elections is far from certain, some corporations have started to anticipate an Obama presidency as they are concerned about possible changes in corporate oversight and fiscal policy.”

Andrew Liveris, the chief executive of Dow, said: “The transaction delivers on the promises we have made to our shareholders about transforming our earnings profile to one of high-growth and less cyclicality.”

Rohm and Haas makes products that range from adhesives and cement additives for the construction industry to organic acids and taste additives for food. The company was founded by Otto Rohm and Otto Haas, two German engineers, in 1907 and is based in Philadelphia.

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