Here's the heart of the 9th circuit court's decision in the
California recall election postponement--based on the
"equal protection" clause of the 14th amendment:

"Plaintiffs argue that the use of defective voting systems creates a substantial risk that votes will not be counted. In addition, they claim that the use of defective voting systems in some counties and the employment of far more accurate voting systems in other counties denies equal protection of the laws by impermissibly diluting voting strength of the voters in counties using defective voting systems. In short, the weight given to votes in non-punchcard counties is greater than the weight given to votes in punchcard counties because a higher proportion of the votes from punchcard counties are thrown out. Thus, the effect of using punchcard voting systems in some, but not all, counties, is to discriminate on the basis of geographic residence.

This is a classic voting rights equal protection claim. As the Supreme Court explained in Bush [v. Gore, 2000], “‘the right of suffrage can be denied by a debasement or dilution of the weight of a citizen’s vote just as effectively as by wholly prohibiting the free exercise of the franchise.’” 531 U.S. at 105 (quoting Reynolds, 377 U.S. at 555). Further, the “‘idea that one group can be granted greater voting strength than another is hostile to the one man, one vote basis of our representative government.’” Id. at 107 (quoting Moore v. Ogilvie, 394 U.S. 814, 819 (1969)).

As the Court stated much earlier in Wesberry v. Sanders, 376 U.S. 1, 8 (1964), “To say that a vote is worth more in one district than in another would . . . run counter to our fundamental ideas of democratic government . . . .” Plaintiffs’ equal protection claim is much the same as the one in Gray v. Sanders, 372 U.S. 368 (1963). That case involved a Georgia county unit voting system that weighted rural county votes more heavily than urban county votes and weighted the votes from some small rural counties more heavily than larger rural counties. The Supreme Court held that this constituted a violation of the Equal Protection Clause, writing that “once the class of voters is chosen and their qualifications specified, we see no constitutional way by which equality of voting power may be evaded.” Id. at 381. As the Court put it: “Every voter’s vote is entitled to be counted once. It must be correctly counted and reported.” Id. at 380. Gray echoed Reynolds’ admission that “the basic principle of representative government remains, and must remain, unchanged – the weight of a citizen’s vote cannot be made to depend on where he lives.” Reynolds, 377 U.S. at 567. As the Court noted: “A citizen, a qualified voter, is no more nor no less so because he lives in the city or on the farm. This is the clear and strong command of our Constitution’s Equal Protection Clause.” Id. at 568. In short, the Equal Protection Clause requires “the opportunity for equal participation by all voters in the election . . . .” Id. at 566."

Of course, I could use findlaw to look up all these cases, but I'll leave that to you, dear reader.