2008: the first presidential election between two sitting members of Congress?

[Mr. Morden]

Barring some extraordinary circumstances, John McCain, a sitting US senator, will win the 2008 GOP nomination, and face off in the general election against a Democratic candidate who is also a sitting US senator.

Is this the first presidential election in American history in which both of the two major party candidates were sitting members of either house of Congress at the time of the election?  I can't think of another one.

In fact, I can't even think of another case in which both candidates had served in their most recent public office as a member of Congress (meaning that both candidates were either current members of Congress or former members who had no executive branch jobs since leaving Congress), except 1860.,,,which is kind of an odd case, because of there being more than two major candidates.

[Mr. Morden]

is there no chance McCain would resign the Senate?  like Dole, '96?  it'd give him a good talking point against Clinton or Obama about how they aren't doing their job since they are always on the campaign trail.

I think it's unlikely, especially since a Democrat would name his replacement.  Not a great way to keep the peace with conservatives.  Dole was also Senate Majority Leader, so it was harder to keep focus on his job in the Senate while he was campaigning.  If you're just 1 of 100 Senators though, it's less of a big deal if you're distracted.