The Hotline, as usual, explains the political connotations:
If Sen. Johnson decides he is too ill to continue as Senator, Gov. Mike Rounds (R) would have ten days from the day of Johnson's resignation to appoint a replacement.
Because Johnson's in cycle, his replacement would stay on through the '08 elections.
Rounds was the guy who wanted to outlaw abortions even if the mother had been raped, by the way, and the people of his state voted him down. Don't think that he is feeling particular democratic (or Democratic) these days and would appoint ex-Sen. Daschle or US Rep. Hereseth to replace Johnson. I would pick South Dakotan Tom Brokaw.
The Third Avenue prays for Johnson's speedy recovery. "Bill Press is making a very important point: GWU Hospital has a world-class stroke unit and is full of top-flite professionals," and that we have no idea how bad a stroke this really is. Let's hope it is extremely minor or just a rumor.
UPDATE: The Washington Post version of the story makes it seem like it was a relatively minor stroke.
Johnson had become disoriented during a call with reporters, stuttering in response to a question. He appeared to recover, asking if there were any additional questions and then signing off.
LATE UPDATE: CBS News: Julianne Fisher,a spokeswoman for Senator Johnson, "said the senator did not suffer a stroke or heart attack." Thank goodness. It seems like he started stuttering during the press event, and felt weird, so out of abundance of caution, his staff rushed him to the best stroke place in the area. Hat tip-- Think Progress