A candidate's strengths can also be his weaknesses. Take the case of Rick Santorum.
One of his strengths is perseverance. For more than a year, he made hundreds of appearances in Iowa, New Hampshire and South Carolina, with no visible result in the polls.
He persevered and ended up finishing first in the Iowa caucuses on Jan. 3. Then, after poor showings in New Hampshire, South Carolina, Florida and Nevada, he finished first in Missouri, Minnesota and Colorado on Feb. 7.
Now he's leading Mitt Romney in most polls nationally and in Romney's native state of Michigan.
Santorum's other strengths include spontaneity and authenticity. His speeches are unscripted, and he answers, often at considerable length, every question at campaign events.
And those answers are sometimes not what any competent political consultant would recommend. Which is where Santorum's strength becomes a weakness.
Example: In an interview last October with the evangelical blog Caffeinated Thoughts, Santorum said, "One of the things that I will talk about that no president has talked about before is I think the dangers of contraception in this country." Contraception, he went on, is "not OK."
"Maybe people don't want us to talk about those things," he added. And he has said later that he doesn't seek a ban on contraceptives -- a good thing, since that was ruled unconstitutional by the Supreme Court in Griswold v. Connecticut 47 years ago.
But by bringing the subject up, he guaranteed that he would be peppered with questions about the issue by the likes of ABC's George Stephanopoulos and CBS's Bob Schieffer.
More recently Santorum opined that Barack Obama had a "phony theology." The context showed he was referring to Obama's environmental policies, and he later said he doesn't doubt the president's claim to be a Christian. But his ad libbed use of the word "theology" inevitably caused controversy.
No one can doubt that his opposition to contraception and his recent denunciations of prenatal testing and women in combat reflect his deep moral and religious beliefs.
But they also allow opponents to pigeonhole Santorum as a religious conservative despite his considerable record on and knowledge of economic and foreign policy issues.
It is political malpractice to give opponents such an opening in a year when voters are overwhelmingly focused on the economy and the Obama Democrats' vast expansion of the size and scope of government.
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