Only once during the 20th century -- 1956 -- did a Republican win the White House without carrying the state of Missouri. So is it problematic, then, that the three leading Democratic presidential candidates lead in every potential matchup against the four leading Republican presidential candidates in the Show Me state? Take a look at the latest numbers from Research 2000:

On average, the Democratic candidates lead the Republican candidates 46.5 percent to 39.2 percent in Missouri. On the basis of these numbers I wouldn't mark the state down in the Democrats' column just yet. Note for instance that John Kerry got about 46 percent of Missouri's vote in 2004 and that Al Gore got about 47 percent in the state in 2000 -- and neither of them carried the state.

That said, George W. Bush got 51 percent of Missouri's vote in 2000 and 53 percent in 2004, a significantly higher share than the Republicans' current showing in the low 40s, indicating that the Republicans have a lot of ground to recover before they are able to carry this state. And though I wouldn't use history to suggest that the GOP needs Missouri's support in order to win the White House, the electoral vote math gets really difficult for the party if it can't win Missouri -- particularly if states like Virginia, Arkansas and Ohio start going Democratic, as polling indicates they might.