A new Kansas City Star poll shows Donald Trump leading Ted Cruz 36 percent to 29 percent in Missouri's Republican presidential primary. Marco Rubio and John Kasich are far behind in the single digits at 9 percent and 8 percent, respectively.

With just a few days to go until the March 15 primary, the poll finds that 17 percent of Missouri GOP primary voters are still undecided. It wouldn't be too difficult for Cruz to overtake Trump if undecided voters break his way and some Rubio and Kasich supporters conclude Cruz is the only viable alternative to Trump in Missouri. Cruz has defeated Trump in three neighboring states this year: Iowa, Kansas, and Oklahoma.

The Missouri primary has received far less attention in the press than the purely winner-take-all March 15 primaries in Ohio and Florida, but with 52 delegates up for grabs the Missouri primary is very important. Ohio only has 14 more delegates than Missouri.

In Missouri, 12 delegates will be awarded to the statewide winner, while the remaining 40 delegates are awarded on a winner-take-all basis in each congressional district (five delegates apiece for each of the state's eight congressional districts).

While polling shows that Cruz is the only candidate who can stop Trump in Missouri, it also shows that John Kasich is the only Republican running neck-and-neck with Trump in Ohio, and Marco Rubio is the only candidate who has a shot at beating Trump in Florida.

The picture is a little more complicated in Illinois, where most delegates are elected by each congressional district. Cruz is thought to have a better shot at beating Trump downstate while Kasich or Rubio may be stronger candidates in the Chicago suburbs.

If Trump sweeps the March 15 contests, he'll be in a strong position to win the Republican nomination, but even a mixed result could make it difficult for Trump to get the majority of delegates necessary to win the nomination.