The options for Delaware Republicans on September 14 are nominating Christine O’Donnell or Mike Castle to be their Senate nominee.

O’Donnell, if nominated, will have (cough) an uphill climb in a state where registered Democrats outnumber registered Republicans roughly 329,000 to 179,000.

Castle has consistently led all polls and his voting history suggests he will vote with conservatives 52 percent of the time or so. If Democrat Chris Coons is elected and votes in a pattern similar to Delaware’s other senator, he will vote the conservative position 12 percent of the time; if he emulates current Democratic senator Ted Kaufman, he will vote the conservative position 4 percent of the time.

Over his 17 complete years in the U.S. House of Representatives, Castle has voted the conservative position, as defined by the American Conservative Union, about 52 percent of the time. In 2009, ACU scored Castle at 56. So how did he get that rating from the group last year?

Castle opposed the Lilly Ledbetter pay act, which the ACU described as a “new Pandora’s Box for trial lawyers.” He voted for a January 2009 bill that would prevent the Treasury from spending the $350 billion that remained in the TARP program. He opposed the Obama stimulus. He voted against efforts to water down legislation barring federal funds to ACORN or other organizations that employ people who have been convicted of election-law violations. He voted to eliminate the earmark for the airport near Johnstown, Pa., named after Rep. John Murtha. He voted to cut discretionary government spending in the appropriations for the Departments of Housing and Transportation by 5 percent.

He supported an amendment to the health-care bill that would ban using taxpayer funds to provide abortion services, an interesting vote for a self-described pro-choice Republican. He voted against the health-care bill.

A central point of the O’Donnell folks is that Mike Castle is unacceptable because he doesn’t support the repeal of Obamacare. But that’s only half his stated position. Castle thinks trying to repeal Obamacare while Obama is president is a waste of time, but he’s open to the idea if the GOP can regain control of the White House:

(This is not some new position shift, spurred by the impending primary; the video above is from April. Ironically, if Castle is nominated, it is possible Delaware Democrats will urge voters to oppose Castle because of his willingness to repeal Obamacare.)

Now, we can argue about whether this is a wise strategic assessment or a poor one, but Castle’s sense that any repeal effort would be unable to overcome a presidential veto does not make him a de facto Obamacare supporter. For what it’s worth, I don’t see this as an either-or proposition; if the GOP tries and fails to overcome an Obama veto, they can always try again in January 2013 if a Republican wins the presidency two years from now.

He voted to extend the repeal of the estate tax and opposed making the new estate-tax rates permanent. He voted for a bill to repeal the TARP program and lower the federal debt limit. Finally, he voted against the financial-industry-regulation legislation backed by Barney Frank.

Because Delaware has only one representative in the House of Representatives, we have no House Democrat from that state to compare against Castle’s voting record, but in all of the above votes, the vast majority of Democrats took the opposing position.

Jeff Lord argues, “Mike Castle plays for the other side [meaning Democrats] wearing the Republican jersey.” But the terms “not as conservative as I would like” and “Democrat” are not synonyms, no matter how much we pound the table or how loudly we insist it is so.

O’Donnell fans complain about Castle by pointing to his record. We know what kind of a legislator Castle will be, warts and all, because of his record. With Christine O’Donnell, all we have are promises. We can’t evaluate her on her record in elected office because she has no record. O’Donnell seems determined to begin her political career by winning a U.S. Senate seat; she has never served in a local board of education, town or city council, state legislature, etc. Her next general-election victory will be her first.

UPDATE: The winner in this election will be seated immediately, not in January. Phil Kerpen, vice president for policy at Americans for Prosperity, writes in to note that on the lame-duck session, Castle and O’Donnell are synonymous:

Delaware is holding a special election for the unexpired four years of Vice President Joe Biden’s term, and insurgent tea party candidate Christine O’Donnell has made a promise to stop the lame duck-agenda a centerpiece of her primary campaign against moderate Republican Mike Castle. O’Donnell has been vocal in her opposition to policies like cap and trade, card check, and tax hikes which are on the lame-duck agenda. She has made a clear public commitment to oppose any major policy changes in a lame-duck session.

Castle recently matched her promise to stop the lame-duck agenda. I asked his staff for a statement from Castle on the lame-duck session and they provided this very strong statement from the congressman: “The only business that should be conducted during a lame-duck session of Congress is keeping the government running until the newly elected legislators are sworn in. I do not agree with those who say this period of time should be used for passing controversial legislation and would not play a role in helping to circumvent the will of American voters.”

. . . Democrat Chris Coons has been silent on the lame-duck issue.