I don't think it's ever been done, although I believe it's possible: has a major party candidate ever run for POTUS without appearing on all the states ballots?
Outside of Abraham Lincoln in 1864, I can't think of any others. And 1864 was a special case, to be sure.
So would the DNC try to run Soetoro in say, 40 states instead of 50, if 10 states passed a proof of eligibility law? If that doesn't prove Soetoro is ineligible, I don't know what does.
Thoughts/comments?
You meant Lincoln in 1860.
...and Fremont in 1856. All the Southern and border states kept the first & second GOP Presidential candidates off the ballot.
Yes, if a state kept Obama off the ballot because of constitutional eligibility it would definitely allow Obama to take the issue to court, although if only one or two GOP states do it Obama may choose to ignore it (even if he was actually born in Hawaii) so as not to risk the court declaring him ineligible.
As for a major-party presidential candidate not being on the ballot in a state, it has happened more often than you think. Incumbent President Lyndon Johnson was not on the ballot in Alabama in 1964 (Goldwater carried the state, and “unpledged Democrat electors” finished second), and incumbent President Truman was not on the AL ballot in 1948 (Strom Thurmond was the nominee of the AL Democrat Party and carried the state). In 1912, incumbent President Taft was not on the ballot in SD, while former President Theodore Roosevelt, nominee of the Progressive (”Bull Moose”) Party and second-place finisher that year was not on the ballot in OK (the only two presidential candidates on the ballot in all 48 states that year, and thus the first in history to be on 48 state ballots, were Democrat Woodrow Wilson and Socialist Eugene Debs). And in 1892, former President Grover Cleveland gained back the White House despite not being on the ballot in a few states out West in which Populist Party candidate James Weaver was stronger than Cleveland and was the “fusion candidate” against Republican President Benjamin Harrison. Off the top of my head I can’t think of any other post-1860 major-party nominee to be denied ballot access, but maybe there were one or two others as well.
Oh and to Answer your question. I don't think it's ever been done, although I believe it's possible: has a major party candidate ever run for POTUS without appearing on all the states ballots?
Yes. There are cases since 1860 and 1864. Sort of. The parties appeared but with different candidates.
In 1912 Taft was the GOP nominee. But in South Dakota TR had the GOP ballot line and Taft did not appear. In Cali TR had the GOP and Progressive Lines, Taft only got write in votes. TR conversely didn't appear on the Oklahoma ballot.
In 1948 Strom Thrumond had the official democrat line in Alabama. Harry Truman wasn't on the Alabama ballot. Thrumond also had the dem line in Mississippi but Truman appeared as a "National Democrat".
In 1964 also in Alabama LBJ did not appear on the ballot. Only Goldwater and a slate of "unpledged" democrat electors.