The Super Tuesday results make it clear that Donald Trump can still be beaten yet also make it seem less likely that his Republican rivals will ultimately bring him down.

He holds only 36 percent of the popular vote in the returns counted so far; 39 percent if you exclude Ted Cruz’s home state, Texas. It’s a low enough number to believe he could still lose the nomination if the field narrowed to a one-on-one race.

But a one-on-one contest between Trump and anyone else now seems less likely to develop soon, particularly before the winner-take-all states March 15. The results cement Trump as a very clear front-runner for the Republican nomination.

One win for Rubio

The night could not have gone much worse for Marco Rubio, perhaps the only Republican with a good chance to beat Trump in a one-on-one contest. He failed to win Virginia, his best prospect of a primary victory. He has won in Minnesota, but it will be hard for him to claim any great strength with one caucus win in what was already poised to be his best state.

Even worse for Rubio was the strength of his opponents. Cruz won Texas and neighboring Oklahoma, giving him more wins than anyone else in the race except Trump. Cruz did not finish in a distant third elsewhere in the South, as seemed possible soon after South Carolina.

Between his own failings and Cruz’s strength, Rubio seems likely to be in a distant third place in the delegate count after Tuesday. Rubio is also in danger of missing crucial delegate thresholds in Texas, Vermont, Alabama and perhaps Tennessee.

Kasich beats Rubio in Vermont

Making matters worse for Rubio is that John Kasich, who has very little support nationwide, nonetheless managed to defeat him in Vermont and might still do so in Massachusetts. Kasich won 9 percent of the vote in Virginia, probably throwing the state to Trump. His support was strongest in places like Northern Virginia, where Rubio fared best.

Cruz, despite his strength in the South, fared poorly elsewhere. It bodes poorly for his chances in the rest of the campaign, which will mainly be fought in much more challenging territory than the Southern-heavy slate of states Tuesday night.

Trump on a roll with time running out

Still, with Cruz and Kasich beating or exceeding expectations, and Rubio failing to counter with strength of his own, it is hard to imagine either Kasich or Cruz leaving the race soon.

Yet there’s not much time for a single candidate to emerge before Trump takes a big and perhaps insurmountable lead.

By March 15, nearly 60 percent of all the delegates to the Republican nomination will have been awarded. On that date, five large states will cast ballots, and several, including Florida and Ohio, are winner-take-all states. Illinois and Missouri award their delegates in a way that will most likely assure a lopsided margin for the victor.

If Trump isn’t defeated on that date, he will be in a very strong position to amass a majority of delegates by the end of the primary season. If Trump had a big day March 15 and then won by even a little afterward, say by a margin as small as 3 percentage points, he would probably end with a majority of delegates — enough to avoid a contested convention.

That’s because the rules become heavily biased toward winners starting March 15; even modest victories with less than a majority of the vote would be enough for Trump to carry a majority of delegates.