However, the Pheu Thai Party, the reincarnation of the PPP, vowed to fight back in a political tug-of-war that intensified shortly after the return to Thailand of Khunying Pojaman Damapong, ex-wife of ousted premier Thaksin Shinawatra.
The Democrat camp managed to attract MPs from Puea Pandin and Ruam Jai Thai Chart Pattana parties, the disbanded Chart Thai and Matchima Thipataya parties and the Friends of Newin faction from the PPP, whose MPs are loyal to banned politician Newin Chidchob.
The new coalition claimed to have at least 250 MPs, which is a majority in the House with 447 MPs remaining in the wake of last week's court verdict disbanding three coalition parties and banning their executives from politics for five years.
The Pracharaj Party and some MPs from Puea Pandin, including party leader Mun Patanothai, remained in the Pheu Thai camp.
Democrat secretary-general Suthep Thaugsuban called a press conference at the Sukhothai Hotel yesterday evening to announce the new coalition. He said the new coalition wanted to push for political changes to meet the wishes of the people.
"We have agreed to form a government to revive the country's economy and confidence," Suthep said after meetings with the PPP's former allies. "We are not doing this for personal or vested interests. No bargaining has been done, and all of us want to cooperate to solve the country's problems."
Sanan Kachornprasart, who represented Chart Thai, said the previous coalition had not been able to run the country effectively so his party had decided to switch sides for the sake of the country.
Ranongrak Suwanchawee said her Puea Pandin Party had decided to do the best thing for the country by switching its allegiance. "All of us agreed that this was the best way to tackle the national crisis. We have made the best choice for Thailand," she said.
Ruam Jai Thai Chart Pattana representative Pattana Wannarat Charn-nukul said his party would adhere to the majority decision. He said he would inform his party of the joint decision of the Democrat and smaller parties.
Pornthipa Nakhasai, a representative of Matchima Thipataya, said her party, seeing that the Pheu Thai could not put together a new coalition, had the right to switch sides. She said it had decided to do so for the sake of the country. Boonjong Wongtrairat, from the Friends of Newin faction, said his group had decided to support the Democrats so that a new government could solve the country's problems.
He then read from a prepared statement, saying that MPs in his group would vote for Democrat leader Abhisit Vejjajiva as the next prime minister and decide whether to join a new political party later.
Meanwhile, leading Pheu Thai members held a press conference at party headquarters to insist on the legitimacy of their party forming a new government and on its ability to muster enough MPs to support the bid.
Deputy House Speaker Apiwan Wiriyachai told the press conference that his group had been informed by some members of the Friends of Newin and Chart Thai leader Banharn Silapa-Archa that they would still support Pheu Thai in a new coalition.
Pheu Thai launched a fierce lobbying campaign yesterday, sources said. The "homeless" MPs, whose groups had pledged allegiance to the Democrats, received phone calls urging them to switch camps.
The sources said that if Pheu Thai could not lure enough MPs to its side, caretaker Prime Minister Chaovarat Chanweerakul would be instructed to dissolve the House of Representatives.
Yet it remained unclear yesterday whether he had the clout to do so. Chaovarat's son Anutin, one of the banned former executives of the disbanded Thai Rak Thai Party, is a close associate of Newin.
If the plan fails, according to the sources, the alternative is for pro-Thaksin red-shirted protesters to besiege Parliament in a bid to obstruct selection of a new premier, a tactic that was used recently by the anti-government People's Alliance for Democracy.