N.Y. Times:
In interviews, many women, citing their own difficulties with less demanding jobs, said it would be impossible for Ms. Palin to succeed both at motherhood and in the nation's second-highest elected position at once.
"You can juggle a BlackBerry and a breast pump in a lot of jobs, but not in the vice presidency," said Christina Henry de Tessan, a mother of two in Portland, Ore., who supports Mr. Obama.
Her thoughts were echoed by some Republicans, including Anne Faircloth, daughter of former Senator Lauch Faircloth of North Carolina. Being a governor is one thing, Ms. Faircloth said, and Ms. Palin's husband, Todd, seems like a supportive spouse. "But running for the second-highest office in the land is a very different kettle of fish," she said.
Many women expressed incredulity — some of it polite, some angry — that Ms. Palin would pursue the vice presidency given her younger son's age and condition. Infants with Down syndrome often need special care in the first years of life: extra tests, physical therapy, even surgery.
In fact, all Palin has to do is campaign until the first week in November. After that, she can spend all the time she wishes with her family. The only constitutional role the vice-president has [besides breaking tie votes as "President of the Senate] is to be available in case the president dies or becomes incapacitated. To be prepared for that, Palin should get occasional briefings on national security issues. Beyond that, the vice-presidency is perhaps the ideal job to "juggle a BlackBerry and a breast pump," because a vice-president need not do anything.
Put another way, unless the vice-president takes on role not constitutionally assigned to her (as recent veeps, most prominently Dick Cheney, have), it's a far less demanding job than being governor of Alaska.
UPDATE: BTW, Obama has two little girls, and given that the president does have real, pressing issues to deal with, as well as an inevitable worldwide travel schedule, it will be far hard for him to be a good dad while president than for Palin to be a good mom while being veep. But that's not really the voters' problem, and it would be foolish to take this into account when voting.