Mitt Romney has tremendous vulnerabilities as a presidential candidate, but those weaknesses won’t matter unless one of his rivals tries to exploit them. Tonight, he skated past questions on the health care law he signed as governor and on his record of flip-flopping on abortion, because none of his opponents were willing to challenge him.

This made for an especially weak showing by Tim Pawlenty, who talked tough in a television appearance on Fox News Sunday when he used the term “Obamneycare” to describe the Obama/Romney approach to health care. But when given a chance, repeatedly, to elaborate, Pawlenty wimped out. In addition to letting Romney get away with his flawed explanations for his disastrous health care legislation in Massachusetts, Pawlenty came off looking weak – like the guy who criticizes you behind your back and cowers in front of your face. It was sort of like Ronald Reagan’s “I am paying for this microphone” moment in New Hampshire, only in reverse.