President Obama marked his 100th day in office this morning with a triumphant press conference alongside the newest Democrat in the Senate.

Arlen Specter, who was elected as the Republican Senator for Pennsylvania, was introduced by Mr Obama as “one tough hombre” the day after he crossed the floor to join the Democratic Party.

The ex-Republican said he would not necessarily vote with the Obama Administration on every issue but he said he would be an asset to the government. The switch puts Democrats closer to the 60-vote supermajority they need to push a radical agenda through the Senate.

Mr Obama was careful to begin his remarks by addressing the swine flu outbreak in America and said the quest for health care improvements made him proud to work with Mr Specter.

The President emphasised Mr Specter’s battle with serious illness, which inspired him to reject the Republican Party’s lack medical reform and investment in research.

“Today I have the honour of standing next to the newest Democratic Senator,” he said. “I am grateful that he is here . . . I am eager to have his counsel and advice.”

Mr Specter, 79, gives the Democrats and their allies at least 59 Senate seats. One vacancy remains from the state of Minnesota, where Al Franken, a Democrat, holds a narrow lead in a race being disputed in courts.

Healthcare and energy reform are looming and Mr Specter was keen to emphasise his support on those issues today. “I think that I can be of assistance to you, Mr President,” he said, claiming it was “scandalous” that America had not done more to use its knowledge in scientific and medical research to help cure the world’s ills.

“I felt comfortable talking to my Republican colleagues yesterday,” he said of the moment he informed them of his defection. “When I talked to the President yesterday I said I haven’t seen you in the [Senate] elevator recently. So I said I was calling him up for a chit chat.”

Mr Specter, who has twice been treated for Hodgkin's disease, said the two men had spoken often when Mr Obama worked in a Senate office close to his. “The President had approached me when he was Senator Obama and he said tell me, Arlen: ‘If a Jewish kid from Kansas can carry Pennsylvania how can a black kid?’”

Although Mr Specter said he had reached the decision to defect gradually, secret negotiations on Capitol Hill and repeated overtures from Vice-President Joe Biden in recent weeks are believed to have tipped the balance.

It is understood that the Democratic leadership has promised to give Mr Specter strong backing – and to discourage others from standing against him - in next year’s Pennsylvania primary and Mr Obama appeared to confirm that today.

The addition of Mr Specter and Mr Franken would give the Democrats a filibuster-proof majority for the first time since 1979 when Jimmy Carter was President.

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