What more to say about Pennsylvania? The Democratic race has become a sitcom, in which all the stock characters — the sassy grandma, the dumb jock, etc. — go through crisis after crisis and never change a bit. Last night, as usual, Clinton won the votes of women, older people, Catholics, and voters without a college education, and Obama won among men, younger people, non-whites, and college graduates.

In particular, the age difference seems irresolvable. According to exit polls at CNN, Clinton won the over-60 vote in Pennsylvania by a ratio of 62-38, while Obama won the under-30 vote by a ratio of 61-39. In all 28 primaries and caucuses for which CNN has done exit polls, Obama has done better with younger voters, and in 17 states Obama has won the under-30 cohort while losing voters over 60. (In another state, California, he tied Clinton among voters under 30 but lost the senior set by 21 points.) The gap has been smallest in Vermont (where Obama won 64 percent of the younger group and 58 percent of the older group) and Connecticut (58 percent and 50 percent). It’s been widest in Iowa (where Obama got 57 percent of the younger group but only 18 percent of older voters against Clinton and John Edwards) and Ohio (61 percent for Obama among younger voters and 28 percent among older voters).

This persistent pattern may spell trouble in November for the Democrats. If Obama is the nominee (still the likelier possibility), he may lose older Democrats to 72-year-old John McCain. If Clinton is the nominee, she may not attract younger voters to the polls and may have problems with independents who don’t necessarily share the fondness for the first Clinton administration that older Democrats seem to have.