Marco Rubio wins the Minnesota Republican primary

Marco Rubio won the Minnesota caucus on Tuesday evening, giving him a lifeline in his long-shot bid to stop Donald Trump from claiming the Republican nomination. The victory will strengthen Rubio's argument that conservatives should rally around him instead of Ted Cruz.

But Rubio has two big problems standing between him and the Republican nomination. One is Donald Trump's commanding lead in other states. Minnesota is Rubio's first win of the primary season, whereas Donald Trump will have close to a dozen wins under his belt by the end of the night. If Rubio is going to wrest the nomination away from Trump, he's going to have to start actually winning a lot more states.

Rubio's other big problem is Ted Cruz. The Texas senator has already won contests in Iowa, Texas, and Oklahoma. Rubio has been arguing for weeks that he's the best choice to lead a united conservative movement against Donald Trump, but it's hard to see why Cruz should get out of Rubio's way instead of vice-versa.

Minnesota is Rubio's only win so far

For weeks, the media have portrayed Marco Rubio as the most potent threat to Donald Trump. But the election results so far haven't born this out. Ted Cruz dealt Donald Trump his first defeat a month ago in Iowa. Then this evening Cruz won two more states — Texas and Oklahoma.

To be sure, Super Tuesday featured a lot of southern states where Cruz can be expected to do well. But the race also featured states like Massachusetts, Vermont, and Virginia that should have been Marco Rubio territory. Yet Rubio fell short in Virginia, and may wind up finishing behind John Kasich in both Massachusetts and Vermont.

Rubio's challenge, then, is to figure out how he can replicate his Minnesota win elsewhere in the country. Right now, it seems like Rubio is losing — not only to Donald Trump but to Ted Cruz as well — and he doesn't even seem to know it.