President and Mrs. Obama’s appearance at Ohio State yesterday carries with it another troubling sign for their party’s prospects this year. Relying on young voters in a midterm election is like looking for a cab at 5 p.m. in the rain. You’re almost certainly going to get wet. First, young adults are much less likely to be registered to vote. In our latest ABC/Post poll, just 58 percent of 18- to 29-year-olds told us they were registered, compared with 90 percent of their elders. Next, young adults who have registered are much less apt to say they’re certain to vote – 53 percent, compared with 80 percent of those 50 and up. We've seen this before. Without a marquee presidential election to grab their attention, midterms just don’t attract young voters. Under-30s accounted for 12 to 14 percent of the turnout nationally in exit polls in midterm elections since 1990, vs. 16 to 20 percent in presidential contests. (What’s looking different for ’10 is higher vote intention among seniors, not a good group for the Democrats this year.) Note too that young voters were not good for Obama in 2008 because they turned out in disproportionately higher numbers; in fact they voted at about their usual share of the electorate. The difference was that those who did vote supported Obama by a remarkably lopsided 66-32 percent. Young voters are House Democrats’ best group this year (D-R vote preference is 56-39 percent among registered voters under 30; insufficient sample size for likely voters that age.) But that does not match Obama’s ’08 margin in this group. And again, the thing about young voters in midterms is that they’re like cabs when you most need 'em. Odds are, they won’t show up. Separately: After its appeal to young voters, the White House today is preparing to issue a report emphasizing the administration's programs aimed at helping women in the economy, such as the Lilly Ledbetter Fair Pay Act, small business loans and new consumer protection programs. There are challenges in this pitch, too. In our latest ABC/Post poll, women disapproved of President Obama's handling of the economy by 52-46 percent, and said by 66-31 percent that the federal government's economic stimulus spending has been "mostly wasted." Ninety percent of women said the national economy is in bad shape. More said it's getting worse than getting better (35 percent vs. 29 percent). And 70 percent said they were dissatisfied with the way the federal government is working.