Presidential Election 1854 - Know-Nothing POTUS

Sep 29, 1854.

President Franklin Pierce has been feeling unwell all day, and now has a severe headache. He decides to go to bed early, hoping to feel better the next day. However, during the night a blood clot reaches his brain, and he dies in the small hours of Sep 30.

This causes consternation. Democrats are distinctly alarmed at the thought of a Presidential canvass on November 7, with the storm over Kansas-Nebraska still raging. Senator (now Acting President) David R Atchison offers a solution. He will recall Congress and have it cancel the election, leaving him in office till 1857.

Congressional Democrats, however, are cool to the idea. They are in enough trouble already over Nebraska, without courting even further unpopularity by such a move. And if they have to face the voters in six weeks time, they don't see why Atchison shouldn't. Also, there is real doubt as to whether Missouri will re-elect him to the Senate. Since the Constitution requires an "officer" to act as POTUS in this situation, can Atchison continue so to act if he loses his seat? And in any case, would they just be putting off the evil day, by allowing time for a still disparate opposition to unite? Is it perhaps better to face the voters now rather than later?

In the end, attempts to change the law are defeated.

So what happens now? Who gets the Democratic nomination, and will it be worth much anyway? Is there enough left of the Whig Party for it to fight a national election? The Republican Party exists, but iirc still only in a few states. Could we get a Know-Nothing in the White House, and if so where do we go from there?