Obama Welcomes Arlen Specter to Democratic Fold

Barack Obama marked the start of his 100th day in office today by formally welcoming to the Democratic party the defecting Republican senator Arlen Specter, a move that could decisively tip the political balance in favour of the president's health, climate change, immigration and other divisive reforms.

Standing alongside Specter in the White House, Obama said: "I am thrilled to have Arlen in the Democratic caucus." He told Specter he did not expect him to be a rubber stamp but he appreciated his battles down the years in favour of public health and other issues.

Their joint appearance, along with the vice-president, Joe Biden, was the first event of a day in which Obama is to fly to the midwest, to St Louis, Missouri, to hold a town hall-style meeting to review his 100 days. He will return Washington for a televised press conference this evening.

In tribute to Specter, Obama said: "Today I have the honor of standing next to the newest Democratic senator from Pennsylvania."

He described him as "one tough hombre", and promised him support in the Democratic primary, virtually guaranteeing he will be the party nominee for the Senate seat in the next election.

Specter potentially offers Obama the crucial vote that will give the Democrats a filibuster-proof majority in the Senate, once the legal battle in the Minnesota Senate race involving Al Franken is resolved.

His defection increases the chances of success for reforms, such as making a start on the creation of a national healthcare system, that would have been vulnerable to Republican opposition.

Specter suggested he could be of assistance, saying he had been deeply involved in healthcare, climate change and immigration.