They say everyone is Irish on St. Patrick's Day, and that will be true two days later as well when Capitol Hill makes its toast to the patron saint of the Emerald Isle on Tuesday.
The annual Friends of Ireland luncheon will be hosted by House Speaker John Boehner, R-Ohio, and attended by President Obama as well as Irish Prime Minister Enda Kenny, and dozens of lawmakers, but many more can claim a right to be present for the event that will feature a performance by Irish Tenors member Anthony Kearns.
There's no official count of Irish-American members of Congress. In fact, Obama himself highlights the difficulty of tabulating Irish lawmakers. The president has Irish ancestry from his mother's side of the family — a fact that Obama only discovered during his 2008 presidential campaign.
Millions of Americans can trace at least faint roots back to Ireland, as Obama did when he visited his eighth cousin, Henry Healy, in Moneygall during a European tour in 2011. (This year, Healy celebrated the real St. Patrick's Day at the White House on Sunday.)
Not every member of the Friends of Ireland group has to be an Irish-American, anyway. Members of Congress representing large populations of Irish descendants have regularly participated, too.
About 11 percent of the respondents in a 2011 census survey identified their primary ancestry as Irish. There are a couple of dozen congressional districts in the country — most of them clustered along the Northeastern coast in Massachusetts, New York, and Pennsylvania — where residents of Irish descent comprise at least one-fifth of the population.
The Cape Cod district of Rep. William Keating, D-Mass., was the most Irish in the 2011 survey, with over a third of residents claiming Irish ancestry.
The number of Catholics in Congress is easier to discern, however.
A study by the Pew Forum on Religion and Public Life found that Catholics comprise the single-largest denomination in both the House and the Senate, though the combined number of Protestants in both chambers is larger. The House is 31 percent Catholic, with 75 Democrats and 61 Republicans identifying themselves as Catholics, while there are 27 Catholic senators (18 Democrats and nine Republicans).
The annual tribute to Ireland used to be fraught with tension during "The Troubles" in Northern Ireland, but its character has changed a lot, said Rep. Peter King, R-N.Y., who is the current leader of the Friends group.
"We had people in the room in the mid-to-late '90s whose supporters were literally killing each other," King said, later adding, "It made the fiscal cliff look like nothing."
"Now it's a pleasure," he continued. "We talk about economic issues. It's much more low-key."
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