The passing of Senator Ted Kennedy leaves a gap as wide as Dunloe for Irish America and the Irish government. Unless we seriously up our game, the Kennedy era will be seen as the zenith of our influence on Capitol Hill.

The welcome mat was always out in office number 317 in the Senate Russell Building where Teddy presided.

Everyone over the years, from county councilors to Northern Ireland leaders to successive Taoisigh (Irish prime ministers), beat a path to the door and they were seldom disappointed. A word from Teddy was enough to secure White House access and the best advice on whatever pressing problems the Irish government and others had.

That era is now over. Irrespective of who replaces him, the next senator from Massachusetts will start off life at the lower end of the food chain in a ferociously competitive environment.

Instead Ireland and Irish America will need to look elsewhere for a champion – and it is not an easy quest. The issue has real urgency, with huge problems such as President Obama's tax legislation that could impact multinational investment in Ireland, and the continuing issue of the Irish undocumented, now exacerbated since the economic down-turn.

The obvious person would have been former Senator Hillary Clinton if she was still in that office. Her replacement, Senator Kirsten Gillibrand, has been paying close attention to Irish community issues in New York but is far too much of a neophyte to count for much yet.

Her New York Senate counterpart, Chuck Schumer, is deeply possessive of his own Irish base in New York and will certainly be a positive influence for Ireland.

Clinton will certainty continue to be a very helpful player from her perch in the State Department, especially as she intends to keep Northern Ireland as part of her brief, but she is also running the world in her spare time for President Obama.

Another obvious person is Senator Chris Dodd of Connecticut, for many years Kennedy's close friend. Dodd owns a house in Connemara, but has his own set of problems. He was recently diagnosed with prostate cancer and faces a very tough re-election battle in his home state in 2010 after persistent allegations of financial improprieties – including how he valued his Irish holiday home.

The most powerful Irish senator on the Democratic side is Patrick Leahy of Vermont, head of the Judiciary Committee, but sometimes to his chagrin, he was utterly overshadowed by Kennedy on Irish issues and may now be reluctant to pick up the mantle.

Many of the candidates on the Democratic side have been courted heavily by the Irish American Democrats, a group set up by Dublin native Stella O'Leary, which has done a superb job focusing senior Democratic Party figures on Irish issues through fundraisers and meetings. Her advice will be sorely needed.

There are leading Republicans who have a real empathy for Ireland. Senator John McCain is one. He was deeply moved by the depth of Irish support for him, including major fundraising, during his campaign with Kennedy to change the immigration laws. His appearances at several Irish Lobby for Immigration Reform rallies in Washington certainly bode well for him as a positive player for Ireland Inc. – but he is still an opposition figure who is getting on in years.

His closest friend on the Republican side, Senator Lindsey Graham of South Carolina, has been a surprise supporter of many Irish initiatives and remains eager to get involved.

There are some up and comers in the House of Representatives too. Congressman Joe Crowley of Queens is number five in the pecking order and much younger than those in front of him and may well be speaker someday.

Congressman Richie Neal, head of the Friends of Ireland in Congress, is another highly placed figure who has been a constant supporter on Irish issues despite being shunned by many Irish governments in the past because of suspicions he was a little too close to Sinn Fein.

But the most obvious candidate is not in the senate at all – though very much a creature of it.

Vice President Joe Biden has a solid Irish Catholic background, from the heartland of Irish America in Scranton, Pennsylvania. He has a deep and abiding knowledge of Irish history, once naming Wolfe Tones as his favorite political hero.

He spent decades in the Senate, was a close confidante of Kennedy and was always available on Irish issues when needed.

Now as vice president he is the most powerful Irish American in politics after Kennedy's death, and he should be an obvious key figure for Irish America and the Irish government.

His powerful office and support may be needed as Obama is showing little signs of seeking to create any unique binds with the Irish.

That was obvious during the first St. Patrick's Day at the White House when the Irish guest list was pared back to the bone to make way for Obama loyalists from Chicago.

The Irish American closest to Obama, Mayor Richard Daley of Chicago, has shown remarkably little interest in his heritage and much more in moving key inner circle personnel into White House positions.

Biden could be a powerful counterweight to all that. The personable former senator from Delaware clearly has a direct line to Obama and – no doubt – could be persuaded to help with Ireland's bidding if the occasion called for it.

But even with the best will in the world, Biden is no Ted Kennedy nor could he ever hope to be.

Ireland lost a great warrior on their behalf when he drew his last breath. In a word he is simply irreplaceable.