Michael Castle is a member of an endangered species in the U.S. Congress: He's a moderate Republican. He's also a key figure in next year's election.
Castle is running to fill the Senate seat for Delaware formerly held by U.S. Vice President Joe Biden, and his likely Democratic foe is Biden's son, Delaware Attorney General Beau Biden.
Castle, a member of the House of Representatives since 1993, is seen as among the Republicans' best bets to end the Democrats' 60-vote super-majority in the 100-member Senate.
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Sixty votes lets Democrats pass legislation without Republican support in that chamber, including a landmark overhaul of the U.S. healthcare system.
"Castle's Senate race promises to be one of the most watched next year," said Jennifer Duffy of the nonpartisan Cook Political Report. "The stakes are high on a number of levels."
The contest unfolds as conservative activists take on Republican moderates like Castle, fueling an internal ideological battle that has pushed the party farther to the right and made it tougher to find common ground with Democrats in Congress.
But these conservatives aren't expected to tangle much, if at all, with Castle in the November 2010 election.
That's because the popular nine-term lawmaker -- who as tiny Delaware's only U.S. representative is elected statewide -- and former two-term governor is seen as the only Republican able to beat Biden in the predominately Democratic state.
"Folks on the right, and frankly I'm one of them in terms of voting record, have to yield to the world as it is and not necessarily how they wish it would be," said Senator John Cornyn, who as chairman of the Senate Republican campaign committee recruited Castle to run.
"The world as it is in Delaware is that if Mike Castle didn't run, Beau Biden would be the next senator from Delaware," said Cornyn.
Still, Castle said he expects to draw "some heat" from conservative activists, like he did at town-hall meetings this year.
At one meeting, he was called a "traitor" for being one of eight House Republicans to back a Democratic bill to fight climate change.
At an another, he was booed for defending President Barack Obama against a conspiracy theory pushed by fringe groups that the Democratic president is not a U.S. citizen.
"There have been times that they have been less than happy with me," said Castle. "And they don't forget."
Castle said Republicans need to be less strident and more tolerant of different points of view if they expect to win back control of Congress and the White House.
"You can't be a majority party unless you are accommodating of that," Castle said. "Democrats have done a better job at that than we have."
Since 2006, the number of House Republicans has dropped to 178 from 232. Many who left were moderates. Some retired, while others were ousted by moderate-to-conservative Democrats.
A decade ago, more than a dozen Senate Republicans were viewed as moderates. Currently, some analysts believe there are just two true moderates, Olympia Snowe and Susan Collins, both of Maine.
Over the years, Castle has bucked Republicans on a number of fronts, such as by voting to raise the minimum wage, bar oil drilling in Alaska's Arctic National Wildlife Refuge and expand stem-cell research.
Yet Castle has joined Republicans in opposing much of Obama's agenda, including a $787 billion economic-stimulus package and legislation to revamp the healthcare system.
"Republicans who oppose Republicans sometimes don't understand that even those of us who are more moderate are going to vote with the party 75 to 85 percent of the time," Castle said.
Conservative activists have gone after Republicans in Congress, charging that they have become enablers for Democrats when it comes to big spending.
"The Republican Party is becoming more and more ideologically pure, and unwilling to work with the other party on anything," said James Thurber of American University's Center for Congressional and Presidential Studies.
In November, right-wingers drove out a Republican nominee in a congressional election in New York, branding her as too moderate. Her conservative replacement lost to a Democrat.
Earlier this year, Senator Arlen Specter, a moderate under fire from conservative activists back home in Pennsylvania, bolted the Republican Party and became a Democrat.
The anticipated Senate race between Castle and Biden is seen as a toss-up. Biden returned in September from a nearly year-long deployment in Iraq as a member of the Army National Guard. He is expected to soon announce his Senate candidacy.
Castle acknowledges differences with conservative activists, but sees them siding with him on Election Day.
"If I end up running against Beau Biden and their choice is Beau Biden or me, I think they'll be inclined to vote for me," Castle said.
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